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A   MANUAL 

of 

ANATOMY 


By 

HENRY  ERDMANN  RAt)ASCH,  M.  Sc,  M.  D. 

ASSISTANT  PROFESSOR  OF  HISTOLOGY  AND  EMBRYOLOGY  IN 
JEFFERSON  MEDICAL  COLLEGE;  INSTRUCTOR  IN  ANATOMY  IN 
THE    PENNSYLVANIA    ACADEMY  OF    FINE  ARTS,  PHILADELPHIA 


WITH  329  ILLUSTRATION'S 


PHILADELPHIA    AND   LONDON 

W.    B.    SAUNDERS   COMPANY 

1917 


il 


Copyright,  iqit,  by  W.  B.  Saunders  Company 


DEDICATED 
TO 

MR.  DANIEL  BAUGH 


PREFACE 


This  book  was  originally  intended  as  a  Visceral  Anatomy  for  the 
use  of  first-year  medical  students.  Although  there  are  numerous  and 
excellent  anatomies  published,  they  are  all  large  and  voluminous. 
There  being  a  need  for  an  anatomy  of  intermediate  size,  the  original 
manuscript  has  been  enlarged  at  the  suggestion  of  the  publishers. 
Chapters  in  Osteology,  Syndesmology,  and  Myology  have  been 
added  and  the  chapters  on  the  Blood-Vascular  and  Nerve  Systems 
have  been  extended  so  as  to  include  the  appendages  and  their 
plexuses,  thereby  making  this  work  desirable  for  medical  students, 
medical  preparatory  students  and  nurses. 

The  anatomy  and  histology  of  the  nerve  system  is  taken  up  in  a 
manner  different  from  that  used  in  most  anatomies.  The  external 
anatomy  is  continued  from  one  segment  to  another,  uninterruptedly, 
and  the  histology  is  taken  up  in  the  same  manner.  In  this  way  the 
student  has  a  more  connected  idea  of  the  parts  and  their  relations 
to  one  another.  In  addition  the  various  pathways  are  given  sepa- 
rate and  rather  full  consideration,  so  that  impulses  may  be  traced, 
in  a  connected  manner,  from  origin  to  termination. 

The  semilunar  valves  of  the  aorta  and  pulmonary  artery  are 
described  in  all  anatomies  under  the  ventricles,  without  justification 
from  a  standpoint  of  anatomy  and  embryology.  In  this  work  they 
are  described  in  their  respective  vessels,  where  they  should  be 
taken  up. 

Although  the  B.  N.  A.,  as  a  whole,  is  not  all  that  could  be  desired 
this  nomenclature  is  given  in  parentheses.  The  author  has  used  the 
terms  ventral  and  dorsal  instead  of  anterior  and  posterior,  respec- 
tively, in  order  to  avoid  confusion  arising  between  anatomists 
and  embryologists.  The  latter  use  the  terms  anterior  and  posterior 
exclusively  for  head  and  tail  directions,  and  not  synonymously  with 
ventral  and  dorsal.  For  this  reason  the  author  uses  cephalad  and 
caudad  for  headward  and  tailward,  discarding  anterior  and  posterior 
altogether  and  avoiding  confusion  arising  in  comparative  anatomy. 

The  illustrations  of  the  first  three  chapters  are  from  Sobotta  and 
McMurrich's  work.  Many  of  those  of  the  visceral  portion  are 
adapted  from  standard  works  as  Cunningham,  Gray,  Piersol,  Morris 
and  Rauber-Kopsch.  A  number  of  the  illustrations  were  made 
from  photographs  of  organs  and  preparations  at  the  Daniel  Baugh 
Institute  of  Anatomy  and  Biology. 
13 


14  PREFACE 

The  author  desires  to  thank  Dr.  J.  J.  Fauz  for  his  assistance  in 
the  preparation  of  the  photographs  and  some  of  the  drawings  and 
Mr.  Smoczynski  for  his  assistance  in  the  preparation  of  the  outlines 
of  the  organs;  also  the  publishers  for  their  suggestions  and  many 
courtesies. 

H.  E.  Radasch. 

Malvern,  Pa., 

July,  191 7. 


CONTENTS 


CHAPTER  I 

Page 
Osteology 17 

CHAPTER  II 
Syndesmology 108 

CHAPTER  III 
Myology 143 

CHAPTER  IV 
Blood-Vascular  System 211 

CHAPTER  V 
Lymph-Vascular  System • 252 

CHAPTER  VI 
Respiratory  System 271 

CHAPTER  VII 

Alimentary  Tract 282 

CHAPTER  VIII 
Urinary  System 316 

CHAPTER  IX 
Male  Organs  of  Reproduction ....   324 

CHAPTER  X 
Female  Organs  of  Reproduction 330 

CHAPTER  XI 

Ductless  Glands 338 

IS 


CONTENTS. 
10 

CHAPTER  XII 

Eyeball  and  Lacrimal  Apparatus. 

CHAPTER  XIII 


Page 

■    341 


CHAPTER  XIV 

358 


\i  1  \  1    System 


A  MANUAL  OF  ANATOMY 


CHAPTER  I 
OSTEOLOGY 


The  skeleton  is  a  framework  of  bone  and  cartilage  that  serves  for 
the  attachment  of  the  muscles.  The  axial  portion  comprises  the 
head  and  trunk  and  is  comparatively  rigid  or  fixed,  while  the  appen- 
dicular portions,  the  appendages,  are  extremely  mobile;  the  bones  of 
the  extremities  represent  a  system  of  levers  actuated  by  the  muscles 
and  acting  upon  the  joints,  which  constitute  the  fulcra.  The  human 
skeleton  is  an  endoskeleton  which  is  more  or  less  completely  invested 
by  the  muscles  and  completely  covered  by  the  skin. 

The  adult  skeleton  comprises  206  individual  bones  arranged  as 
follows: 

Single  bones    Pairs   Total 
f  The  vertebral  column  26  .  .    26 

The  ribs  12     24 

Axial  Skeleton j  The  sternum  1  1 

The  skull  6  822 

I  The  hyoid  bone  1  1 


/  Pectoral  appendage  32     64 

Appendicular  Skeleton'   D  ,   .  , 

rr  l  Pelvic  appendage  31     62 


Auditors-  Ossicles  366 

206 

Bone  is  a  derivative  of  the  mesoderm  and  represents  the  most 
highly  differentiated  of  the  connective  tissues.  It  is  mainly  a  sec- 
ondary tissue  as  in  most  instances  it  is  derived  from  cartilage.  It 
consists  of  cells  and  intercellular  substance.  The  latter  is  a  hard, 
tough  resistant,  yet  elastic  substance  to  which  the  peculiar  charac- 
teristics of  bone  are  due.  Osseous  tissue  consists  of  about  66  per 
cent,  of  inorganic,  or  earth  salts  and  of  34  per  cent,  of  organic  mate- 
rial. The  inorganic  salts  comprise  phosphates,  carbonates  and 
fluorid  of  calcium,  also  chlorid  of  sodium  and  phosphate  of  mag- 
nesium. The  organic  material  includes  fats,  collagen,  etc.  If  a 
fresh  bone  be  burned  or  calcined,  the  organic  material  will  be  re- 


l8  OSTEOLOGY 

moved  and  a  porous  cast  of  the  bone,  representing  the  earthy  salts, 
will  remain.  If  a  bone  be  subjected  to  the  action  of  a  mineral  acid, 
the  earthy  material  is  removed  and  flexible  bone,  representing  the 
organic  substances,  remains.  The  elasticity  and  toughness  of  the 
bone  is  due  to  the  organic  substance  while  the  inorganic  salts  impart 
hardness  to  it. 


.  *■< 


Fig.  I. — Portion  of  a  cross-section  of  a  decalcified  human  radius.  X  about  4.8. 
(Sobotta  and  Huber,  "  Atlas  of  Human  Histology.)  The  figure  shows  the  lamellar  systems  of 
compact  bone,  as  well  as  some  trabecular  of  spongy  bone,  agl,  periosteal  lamellar;  igl,  peri- 
medullary  lamellae;  il.  interstitial  lamellar,  hi.  Haversian  lamellar;  p,  periosteum;  sp,  trabec- 
ular of  spongy  bone. 

Fresh  bone  upon  examination  shows  the  presence  of  an  enveloping 
membrane,  the  periosteum.  This  is  tough,  does  not  strip  readily 
and  serves  for  the  attachment  of  muscles  and  tendons.  The  articu- 
lar portions  of  a  bone  are  covered  with  hyalin  cartilage.  Cleaned 
specimens  are  devoid  of  these  two  structures. 

In  order  to  study  bone  under  the  microscope  it  must  be  decalcified 
and  sectioned,  or  pieces  must  be  ground  so  thin  that  their  structure 
is  readily  discernible. 


STRUCTURE    OF   BONE  19 

There  are  t-dio  varieties  of  bone,  compact  and  cancellous. 

The  compact  variety  is  the  more  abundant  and  exhibits  a  char- 
acteristic structure.  Surrounding  all  bones  there  is  a  fibrous  sheath, 
the  periosteum.  This  consists  of  white  fibrous  connective  tissue  and 
its  deep  layer  is  rich  in  blood-vessels  and  cells,  the  future  osteoblasts. 
From  its  inner  layer  bundles  of  fibers  (Sharpey's)  penetrate  the 
bone.  The  real  osseous  tissue  is  arranged  in  four  varieties  of 
lamellae  and  between  the  lamellae  are  the  lacunae  and  canaliculi. 

1.  The  periosteal  lamella  are  few  in  number  and  lie  just  beneath 
the  periosteum.  These  constitute  the  circumference  of  the  bone 
and  between  them  are  the  lacunae,  containing  osteoblasts,  and  the 
canaliculi.  Howship's  lacuna  are  on  the  surface  and  canals  (Volk- 
mann's)  pierce  the  layers  and  transmit  blood-vessels  for  a  short 
distance. 

2.  The  Haversian  lamella  are  hollow  cylinders  of  bone  that  fit 
into  one  another,  the  central  one  containing  the  Haversian  canal. 
The  number  in  a  system  varies  from  three  to  eight.  Between  the 
layers  are  the  lacunae  and  canaliculi.  The  Haversian  canals  of  the 
various  systems  anastomose  with  one  another.  These  canals  are 
for  the  transmission  of  blood-vessels. 

3.  The  intermediate  lamella  fill  in  the  areas  between  the  cylindrical 
Haversian  systems.  They  are  irregular  in  course  and  contain 
lacunae  and  canaliculi. 

4.  The  perimedullary  lamella  are  irregular  in  number  and  extent 
and  when  present  they  are  seen  on  the  marrow-cavity  surface  of  the 
bone  and  are  comparable  to  the  periosteal  lamellae. 

The  lacuna  are  irregular,  stellate  spaces  and  contain  the  osteo- 
blasts. The  canaliculi  serve  to  connect  the  various  lacunae  together 
and  to  support  the  processes  of  the  osteoblasts. 

An  osteoblast  is  an  irregular,  stellate  cell  with  a  flattened  body. 
Its  processes  are  numerous,  but  short  and  heavy.  These  cells  have 
to  do  with  the  formation  of  osseous  tissue,  but  in  what  manner  they 
do  it  is  unknown. 

Compact  bone  constitutes  the  shafts  of  the  long  bones,  covers  their 
extremities  and  forms  the  outer  portion  of  the  short,  irregular  and 
flat  bones. 

Cancellous  bone  consists  of  delicate  bars  of  osseous  tissue  that 
form  a  network  resembling  a  sponge.  Lacunae,  canaliculi  and  osteo- 
blasts are  present  but  Haversian  systems  are  absent.  This  variety 
is  found  in  the  ends  of  the  marrow-cavity  of  the  long  bones,  forms 
the  bulk  of  the  extremities  of  these  bones  and  of  the  flat,  short  and 
irregular  bones.  This  variety  imparts  lightness  and  permits  of  an 
increase  in  size  without  sacrificing  strength. 

The  medullary,  or  marrow-cavity,  is  long,  narrow  and  contains  the 
marrow;  it  is  found  in  the  shafts  of  the  long  bones.     It  is  lined  by 


20  OSTEOLOGY 

the  endosteum  which  serves  as  an  internal  periosteum  and  a  covering 
for  the  marrow. 

Bone  Marrow. — In  the  adult  there  are  two  varieties  of  bone  marrow, 
red  and  yellow.  In  early  life  only  red  marrow  is  found.  The  red 
marrow  consists  of  a  delicate  network  of  reticulum  connected  with 
the  endosteum.  It  supports  various  cellular  elements  and  blood- 
vessels, nerves  and  lymphatics.     The  cellular  elements  are  as  follows: 

i.  Myelocytes  are  large,  nucleated  masses  of  granular  protoplasm 
that  exhibit  ameboid  movements.  These  are  seen  only  in  marrow 
under  normal  conditions. 


Fig.  2. — Blood.  Elements  of  the  bone-marrow  of  a  mouse.  X  700.  {Sobotta  and 
Huber.  "Atlas  of  Human  Histology.")  The  preparation  was  taken  from  the  femur  of  a  full- 
grown  mouse.  1.  Polynuclear  giant-cell  (myeloplax);  2-7,  marrow-cells;  2,  marrow-cell 
with  annular  nucleus  (goes  through  the  nuclear  stage  of  4  into  that  of  3 — that  is.  into  the 
ordinary  polymorphonuclear  cell") ;  4  and  5.  acidophile  cells;  6  and  7,  mitoses;  8,  ordinary  ery- 
throcyte; o  and  io,  nucleated  erythrocytes. 


2.  Erythroblasts  are  nucleated  red  blood  cells  and  are  very  numer- 
ous as  the  red  marrow  is  practically  the  only  tissue  in  which  they 
are  formed. 

3.  Erythrocytes  are  normal  red  blood  cells  that  have  just  been 
formed  from  the  preceding  and  are  ready  to  go  into  the  blood  stream. 

4.  Leukocytes  are  white  blood  cells  and  are  of  the  finely  and 
coarsely  granular  eosinophilic  and  basophilic  types. 

5.  Myeloplaxes,  or  osteoclasts,  are  large,  irregular  masses  of  proto- 
plasm that  may  contain  one  or  more  nuclei.  They  are  bone-destroy- 
ing cells  and  are  of  great  importance  in  the  growth  and  repair  of 
bone.  They  are  capable  of  ameboid  motion  and  are  also  phagocytic 
in  action. 

6.  Osteoblasts  are  mentioned  in  bone  marrow  but  they  are  chiefly 
at  the  periphery  and  are  not  essential  to  the  marrow. 

Fat  is  seen  in  small  quantities  in  red  marrow  but  predominates  in 
yellow  marrow. 

In  the  adult,  red  marrow  is  found  in  the  extremities  of  the  long 


BONE    DEVELOPMENT  21 

bones  and  in  the  centers  of  the  flat  and  irregular  bones,  or  wherever 
cancellous  bone  is  found. 

Yellow  bone  marrow  is  the  result  of  the  deposition  of  a  great  quan- 
tity of  fat  in  the  red  marrow  of  the  shafts  of  the  long  bones.  As  a 
result  the  cellular  elements  are  greatly  reduced  and  its  function  as 
a  seat  of  blood-cell  formation  is  practically  nil.  It  is  found  only  in 
adults. 

Serous,  or  mucoid  marrow  results  when  the  fat  and  cellular  elements 
are  absorbed  and  replaced  by  a  serous  infiltrate,  as  in  old  age,  starva- 
tion and  certain  diseases.  It  thereby  loses  its  function  of  making 
blood  cells. 

Bone  Development. — There  are  two  methods,  endochondral  and 
mtramembranous. 

In  the  endochondral  form  the  hyalin  cartilage  is  replaced  by  osseous 
tissue.  All  of  the  bones  of  the  body  except  those  of  the  face  and 
vault  of  the  cranium  are  said  to  be  formed  by  this  method  but  the 
endochondral  bones  are  really  formed  by  a  combination  of  the  two 
methods,  as  will  be  seen.  The  point  at  which  bone  formation  first 
begins  is  called  the  center  of  ossification.  There  are  several  of  these 
centers  for  each  of  the  bones  and  these  will  be  considered  later. 

At  the  center  of  a  ossification  the  cartilage  cells  reproduce  rapidly 
and  arrange  themselves  in  rows  parallel  to  the  long  axis  of  the  bone 
(proliferation).  Calcareous  salts  are  deposited  in  the  cartilage 
partitions  and  most  of  the  cartilage  cells  disappear  (calcification). 
New  cells,  chondroclasts ,  appear  and  destroy  some  of  the  partitions, 
forming  a  series  of  small  spaces  called  primary  areola.  Osteoblasts 
gain  access  to  these  spaces  and  lay  down  a  thin  veneer  of  osseous 
tissue  upon  the  cartilaginous  and  calcareous  partitions.  The  peri- 
chondrium becomes  the  periosteum  and  its  cells  form  a  layer  of 
periosteal  bone.  Blood-vessels  and  osteoblasts  penetrate  the  little 
bone  and  enter  the  areolae  which  have  been  converted  into  a  fewer 
number  of  larger  spaces  by  the  destruction  of  many  of  the  partitions 
(vascularization).  The  first,  or  primary  marrow,  is  then  formed. 
The  blood-vessels  and  osteoblasts  proceed  toward  the  extremities 
of  the  little  shaft,  almost  to  the  area  of  proliferation.  Gradually 
all  of  the  calcareous  material  of  all  of  the  partitions  is  removed  and 
replaced  by  osseous  tissue.  After  this  no  more  cartilage  appears  in 
the  changed  area.  Each  extremity  is  ossified  from  an  independent 
center  at  a  later  date  so  that  a  pad  of  cartilage,  the  epiphyseal  disc, 
intervenes  between  the  shaft  and  each  extremity  until  the  bone  has 
reached  its  full  length.  Then  this  disc  ossifies  and  the  parts  are 
united  so  that  this  area  can  no  longer  be  distinguished.  The  bone 
continues  to  grow  in  length  by  cartilage  being  formed  a  little  more 
rapidly,  in  the  epiphyseal  disc,  than  it  is  converted  into  bone.  The 
bone  grows  in  diameter  by  the  continual  addition  of  new  layers  of 


OSTEOLOGY 


periosteal  bone.  After  a  number  of  periosteal  lamellae  have  been 
formed,  osteoclasts  destroy  all  of  the  central  cancellous  bone  and 
establish  the  primary  adult  marrow-cavity.  They  continue  to  de- 
stroy the  oldest  or  innermost  periosteal  lamellae  but  less  rapidly 
than  the  new  ones  are  formed  upon  the  outside.  As  a  result  the 
marrow-cavity  is  formed  and  continues  to  grow  at  the  expense  of 
the  compact  bone  but  never  as  rapidly  as  the  bone  is  formed.  In 
the  meantime  Haversian  systems  are  being  formed  from  the  perios- 
teal lamellae,  and  the  remnants  of  the  latter  constitute  the  irregular 
lamella;. 


PK 


Fig.  3. — Bone  development.  Portion  of  a  longitudinal  section  of  a  metacarpal  bone  of  a 
five-month  embryo.  X  so.  (Sobolta  and  Huber.  "Alius  of  Human  Histology.")  Outside 
in  the  perichondrium  (periosteum)  is  a  layer  of  periosteal  bone.  eK,  bone  formed  by  endo- 
chondral ossification;  A"».  cartilage;  Km,  zone  in  which  the  cartilage  cells  are  arranged  in 
rows;  Km,  zone  of  enlarged  cartilage  cells  and  calcification  of  ground  substance;  KnR, 
remains  of  calcified  cartilaginous  matrix.  M,  marrow;  pK,  bone  formed  by  periosteal  ossi- 
fication; Rz,  giant-cells  (osteoclasts). 

In  the  extremities  of  the  long  bones  and  in  the  flat  and  irregular 
bones  no  marrow  cavity  is  formed.  The  cancellous  tissue  practi- 
cally remains  and  is  added  to  by  the  constant  honeycombing  action 
of  the  osteoclasts  upon  the  innermost  periosteal  lamellae.  In  this 
manner  the  central  portions  of  these  bones  always  remain  cancellous 
and  are  covered  by  only  a  thin  layer  of  compact  bone. 

In  intramembranous  bone  formation  ossification  occurs  without  the 
intervention  of  cartilage.  At  the-  center  of  ossification  (say  of  a 
skull  bone)  the  mesodermal  cells  form  a  membrane  from  which 
fibers  radiate  in  all  directions  and  upon  which  calcareous  material  is 
deposited.  The  inner  and  outer  boundary  layers  of  this  membrane 
become   somewhat   denser   and   constitute   the  periosteum.     These 


CLASSES    OF   BONES  23 

layers  give  rise  to  the  osteoblasts  that  secrete  osseous  tissue  as  above, 
forming  periosteal  lamellae  and  a  veneer  for  the  calcareous  trabeculae. 
More  periosteal  lamellae  are  added  and  the  process  spreads  gradually 
in  all  directions.  The  calcific  material  is  removed  and  replaced  with 
bone  and  osteoclasts  honeycomb  the  innermost  or  oldest  layers  of 
periosteal  bone  thereby  increasing  the  amount  of  cancellous  bone. 
The  thin  covering  of  compact  bone  constitutes  the  tables  of  the  skull 
bones. 

Bones  are  usually  classified,  as  to  shape,  as  long,  flat,  short  and 
irregular.  The  long  bones  (ninety)  are  found  in  the  extremities  and 
include  the  femur,  tibia,  fibula,  humerus,  radius,  ulna,  clavicle,  meta- 
carpal and  metatarsal  bones  and  the  phalanges.  The  name  indi- 
cates the  presence  of  a  central,  more  or  less  cylindrical  portion  called 
the  diaphysis,  or  shaft,  and  two  more  or  less  expanded  portions  the 
epiphyses,  or  extremities.  The  diaphysis  is  a  hollow  cylinder  of 
compact  bone  that  contains  the  yellow  marrow  in  the  adult.  In  the 
longer  examples  of  this  class  the  shaft  is  not  straight  but  curved, 
thereby  greatly  strengthening  the  bone.  The  epiphyses  are  usually 
enlarged  for  articulation  and  muscle  attachment.  Each  consists  of 
a  thin  covering  of  compact  bone  surrounding  a  mass  of  cancellous 
bone  that  contains  red  marrow  throughout  life. 

The  flat  bones  (thirty-eight)  are  the  scapulas,  ossa  coxae,  sternum, 
ribs,  frontal,  vomer,  parietals,  nasals,  lacrimals  and  patellae.  These 
are  adapted  for  protection  and  consist  mainly  of  a  central  mass  of 
cancellous  bone  covered  by  a  thin  layer  of  compact  bone.  In  the 
cancellous  bone  red  marrow  is  found  throughout  life. 

The  short  bones  (thirty)  are  the  carpal  and  tarsal  bones.  These 
serve  to  give  strength  to  the  parts  and  yet  permit  limited  motion. 
Each  consists  of  a  central  mass  of  cancellous  bone,  containing  red 
marrow,  surrounded  by  a  layer  of  compact  bone. 

The  irregular  bones  (thirty-eight)  comprise  the  vertebrae,  tem- 
porals, sphenoid,  zygomatics,  maxillae,  palatals,  conchals,  ethmoid, 
hyoid  and  sacrum.  These  are  very  irregular  in  shape  and  also  con- 
sist of  a  mass  of  cancellous  bone,  containing  red  marrow,  surrounded 
by  a  layer  of  compact  bone.  Some  parts  of  these  bones,  however, 
are  so  thin  as  to  be  nearly  transparent  and  these  portions  contain 
no  cancellous  bone. 

Some  place  the  patellae  and  hyoid  bones  and  the  auditory  ossicles 
(incus,  malleus,  and  stapes)  as  unclassified  bones.  Wormian  bones 
are  found  along  the  cranial  sutures  but  are  inconstant.  Sesamoid 
bones  are  found  in  certain  tendons  of  the  muscles  of  the  extremities; 
they  are  variable  in  number. 

Very  few  of  the  bones  show  extensive  smooth  areas,  but  lines, 
crests,  ridges,  spines,  tubercles,  processes,  protuberances  and  the  like 
are  seen.     On  the  other  hand,  depressions  of  various  kinds,  as  pits, 


24  OSTEOLOGY 

fossa,  cavities,  furrows,  grooves,  fissures,  and  foramina,  or  canals, 
sinuses,  or  air  spaces  are  seen.  Each  serves  its  purpose  as  will  be 
pointed  out  in  each  bone. 

THE  VERTEBRAL  COLUMN  (COLUMNA  VERTEBRALIS) 

The  vertebral  column  comprises  twenty-six  individual  bones  in 
the  adult;  in  early  life  thirty-three  are  present  but  certain  ones  fuse 
as  will  be  indicated  later.  These  bones  are  the  vertebrae  and  they 
are  classified  as  true,  or  movable  and  false,  or  fixed. 

True,  or  movable  False,  or  fixed 

Cervical 7                  Sacrum (5  fused) 

Thoracic 12                 Coccyx (4  fused) 

Lumbar 5 

A  typical  vertebra  comprises  the  body  (ventral  segment ),  the  neural 
arch  (dorsal  segment)  and  a  number  of  processes. 

The  body  [corpus  vertebra-)  is  the  largest  part  but  varies  in  size  and 
form  in  the  different  segments  of  the  vertebral  column.     It  is  nearly 


-spinous  process 


transverse  process 


„     „  ■  „      /.     <         superior  t'crlebral notch 
Superior  articular  pv'rv 

SupfrwrSL7ac\Yjl^\!rarS  ""'  /""' 


Fig.   4. — A  vertebra  seen  from  above. 
(Sobotta  and  McMurrich.) 


Inferior  Ami -fa,  it  hifi 
forkeud  of  rib 


Fir.,    s. — A  vertebra  seen  from  the  side. 
(Sobotta  and  McMurrich.) 


cylindrical  in  shape  and  its  superior  and  inferior  surfaces  are  flattened 
or  slightly  concave,  to  accommodate  the  intervertebral  discs.  Ven- 
trally  and  at  the  sides  the  body  is  concave  from  above  downward, 
as  well  as  from  side  to  side.  The  dorsal  surface  is  concave  from  side 
to  side.  All  parts  exhibit  numerous  foramina  that  transmit  the 
nutrient  vessels  of  the  bones. 

The  neural  arch  (arcus  vertebra)  is  formed  by  the  two  roots  of  the 
vertebra  and  two  lamina.  The  pedicles,  or  roots  of  the  vertebral  arch 
(radix  arcus  vertebra  )  are  two  flattened  bars  of  bone  that  pass  dorsally 
from  the  body  to  the  points  of  attachment  of  the  articular  processes. 
As  these  processes  are  not  of  the  same  height  as  the  body,  a  distinct 


VERTEBRAL    COLUMN  25 

notch  is  formed  between  the  body  and  the  articular  processes,  above 
and  below  these  roots.  These  are  the  superior  and  inferior  inter- 
vertebral notches  {incisurce  vertebra  superior  et  inferior).  In  the  articu- 
lated vertebral  column  these  become  the  intervertebral  foramina  for 
the  transmission  of  the  spinal  nerves  and  vessels. 

The  lamina  are  two,  flat,  rather  broad,  sloping  plates  of  bone  which 
extend  dorsally,  converge  toward  the  midline  and  fuse  with  the  root 
of  the  spinous  process.  These  serve  to  complete  the  neural  arch 
which,  with  the  body,  forms  the  vertebral  or  spinal  foramen. 

The  processes  are  muscular  and  articular.  The  muscular  processes 
are  as  follows:  The  transverse  processes,  two  in  number,  vary  in  size 
and  function  in  the  different  vertebrae.  They  extend  laterally  from 
the  junction  of  the  root  of  the  arch  and  the  lamina  of  each  side.  The 
spinous  process  is  that  mass  of  bone  that  extends  dorsally,  in  the 
median  plane  of  the  body,  from  the  junction  of  the  fused  laminae. 
Its  shape,  size  and  direction  varies  in  the  different  segments  of  the 
vertebral  column. 

The  articular  processes  (zygapophyses)  are  four  in  number,  two 
superior  and  two  inferior.  These  are  placed  upon  the  upper  and 
lower  parts  of  the  neural  arch  at  the  junction  of  the  roots  of  the 
arch  and  laminae.  Each  superior  process  (processus  articularis  supe- 
rior) projects  superiorly  and  faces,  generally,  dorsally.  Each  inferior 
process  (processus  articularis  inferior)  project  interiorly  and  faces, 
generally,  in  a  ventral  direction.  These  directions,  however,  differ 
in  the  various  regions. 

THE   CERVICAL   VERTEBRAE 

The  cervical  vertebras  are  seven  in  number  and  are  the  smallest 
of  the  true  vertebrae.  The  first  and  second  are  considerably  modi- 
fied and  the  seventh  somewhat  so.  In  all,  the  transverse  processes 
are  perforated  by  a  foramen. 

The  body  is  oblong  and  the  dorsoventral  dimension  is  greater  than 
the  transverse.  The  superior  surface  is  markedly  concave  from  side 
to  side  and  slopes  dorsoventrally.  The  lateral  margins  are  sharp 
and  project  superiorly  while  the  ventral  edge  is  rounded  and  smooth. 
The  inferior  surface  is  concave,  dorsoventrally,  and  convex  from  side 
to  side.  The  ventral  edge  overlaps  the  vertebra  beneath.  The 
ventral  surface  of  the  body  is  mainly  flat  but  becomes  concave  at  the 
sides.  The  dorsal  surface  is  flat  and  rough  and  presents  numerous 
foramina.  At  the  superior  part  of  the  lateral  surface  of  the  body  is 
attached  the  transverse  process.  Each  is  pierced  by  the  transvi 
foramen  {foramen  transversarium)  and  consists  of  two  parts,  one 
dorsal  and  the  other  ventral  to  the  foramen.  The  dorsal  portion 
arises  from  the  vertebral  arch  and  represents  the  true  transverse 
process;  the  ventral  portion  represents  the  ribs  of  the  thoracic  region. 


26  OSTEOLOGY 

These  are  united  by  a  small  bar  of  bone  that  completes  the  foramen 
and  each  division  terminates  in  a  small  tubercle  called  tubcrcula 
a ntcr ins  et  posterius.  These  processes  are  grooved  for  the  accommoda- 
tion of  the  spinal  nerve  trunks.  The  vertebral  artery  and  vein  pass 
through  the  transverse  foramina  of  the  superior  six  cervical  verte- 
brae. The  roots  of  the  vertebral  arches  arise  from  the  middle  of  the 
side  (dorsal  portion)  of  the  body  and  are  directed  dorsally  and  later- 
ally, in  a  horizontal  direction.  Above  and  below  these  are  the 
intervertebral  notches.  The  lamina  are  rather  long  and  broad; 
they  fuse  in  the  midline  dorsally.  The  spinous  processes  are  short, 
bifid,  flattened  from  above  downward  and  are  dorsally  directed. 
The  articular  processes  are  dorsal  to  the  transverse  processes.     The 


Fig.  6. — The  fifth  cervical  vertebra  seen  from  above.     (Sobolla  and  MrMurrich.) 


facets  are  circular  and  the  superior  face  upward  and  dorsally,  while 
the  inferior  face  downward  and  ventrally. 

The  Atlas. — This  is  the  first  cervical  vertebra  and  it  possesses 
neither  body  nor  spinous  process.  It  consists  of  two  lateral  masses  con- 
nected to  each  other  by  a  ventral  and  a  dorsal  arch.  Each  lateral  mass 
is  irregular  and  its  ventral  end  is  closer  to  the  midline  than  the  dorsal 
end.  Superiorly  it  possesses  an  oval  articular  facet  {fovea  articular  is 
superior)  that  receives  a  condyle  of  the  occipital  bone.  Each  facet  is 
concave  and  slopes  dorsally  and  toward  the  midline.  The  inferior 
articular  facets  (fovea  artiadares  inferior •&?)  are  circular  and  nearly 
flat.  Each  surface  faces  downward  and  toward  the  midline.  Upon 
the  medial  surface  of  each  lateral  mass  there  is  a  small  tubercle  to 
which  the  transverse  ligament  of  the  atlas  is  attached.  Behind  each 
tubercle  is  a  nutrient  foramen.  The  ventral  arch  (arcus  anterior)  is 
thickest  in  the  middle  forming  here,  on  its  ventral  surface,  the  ventral 
tubercle  (tuberculum  anterior) ;  its  dorsal  surface  exhibits  a  facet  {fovea 
dentis)  for  articulation  with  the  dens  of  the  epistropheus  or  axis. 
The  dorsal  arch  (arcus  posterior)  arises  from  the  lateral  mass  and 
transverse  processes.  At  its  origin  it  is  flattened  from  above  down- 
ward and  bounds  a  groove,  dorsal  to  the  articular  facet,  that  extends 


VERTEBRAL    COLUMN 


27 


to  the  transverse  foramen.  This  groove  is  occupied  by  the  vertebral 
artery  and  suboccipital  nerve.  The  dorsomedian  part  of  the  arch 
may  present  a  small  tubercle  (tuberculum  posterior)  which  represents 
a  rudimentary  spinous  process.  Each  transverse  process  arises  from 
the  lateral  mass  by  two  roots  that  are  united,  enclosing  the  trans- 
verse foramen.  The  anterior  and  posterior  tubercles  are  usually 
fused  into  one.     The  extremely  large  vertebral  foramen  of  the  atlas  is 

Posterior  tubercle 


Transverse  process 

Foramen  transv 


divided  into  two  portions  by  the  transverse  ligament  that  extends 
between  the  two  median  tubercles.  The  smaller  ventral  division 
contains  the  dens  of  the  epistropheus  while  the  larger  dorsal  portion 
accommodates  the  spinal  cord. 

The  Epistropheus. — This  is  the  second  cervical  vertebra  and  it 


Odontoid  process 

(anterior  articular 
facet) 


(epistropheus),  fr. 


.  front.      (Sohotta  and  McMurrich.) 


possesses  a  tooth-like  process  called  the  dens.  The  superior  part  of 
its  body  is  continued  as  the  dens.  The  apex  of  this  process  is  blunt, 
and  to  it  are  attached  the  alar  ligaments.  Where  it  joins  the  body 
of  the  vertebra,  the  process  is  constricted  and  its  dorsal  surface  at  this 
region  is  smooth  and  grooved  to  accommodate  the  transverse  liga- 
ment.    The  ventral  surface  of  the  dens  has  a  facet  for  articulation 


28  OSTEOLOGY 

with  the  dorsal  surface  of  the  ventral  arch  of  the  atlas.  The  inferior 
surface  is  somewhat  concave  and  slopes  sharply  downward  and  over- 
laps the  body  of  the  third  cervical  vertebra.  The  ventral  surface  of 
the  body  is  irregular  and  has  a  ridge  that  extends  onto  the  neck  of 
the  dens.  The  dorsal  surface  is  flattened  and  presents  numerous 
foramina.  The  roots  of  the  vertebral  an  lies  are  deeply  grooved,  in- 
feriorly,  but  superiorly  they  support  the  superior  articular  facets. 
The  laminae  are  short  and  thick  and  form  the  short,  bifid  spinous 
process.  Each  transverse  process  slopes  downward  and  has  but  one 
terminal  tubercle.  The  superior  articular  processes  cover  the  roots  of 
the  vertebral  arches.  They  are  nearly  circular,  flattened  or  slightly 
concave;  they  face  upward  and  a  little  laterally.  Dorsal  to  each  is 
a  groove  in  which  the  second  cervical  nerve  courses.  The  inferior 
articular  facets  are  nearly  circular  and  face  inferiorly  and  forward  or 
ventrally.     These  lie  dorsal  to  the  transverse  processes. 

The  seventh  cervical  vertebra  is  called  the  vertebra  prominens 
because  its  spinous  process  projects  beyond  the  level  of  the  other 
vertebras.  This  process  is  not  bifid.  The  transverse  processes  are 
wider  and  more  prominent  than  those  of  the  sixth  vertebra.  The 
foramen  does  not  usually  transmit  the  vertebral  artery  as  it  is  too 
small.  The  ventral  tubercle  is  small  and  the  costal  element  may  be 
separate,  constituting  a  cervical  rib. 

THE  THORACIC  VERTEBRjE   (VERTEBRA  THORACALES) 

The  thoracic  vertebrae  are  twelve  in  number  and  they  articulate 
with  the  ribs.  The  body  of  a  thoracic  vertebra  is  usually  described 
as  heart-shaped.  The  superior  and  inferior  surfaces  are  slightly 
concave  or  flattened,  smooth  and  rimmed.  The  ventral  and  lateral 
surfaces  are  concave  from  above  downward  and  rough.  The  body  is 
thicker  behind  than  in  front,  thus  forming  the  thoracic  curve  of  the 
vertebral  column  (concavity  ventrally  directed).  Dorsally  it  is 
concave  and  shows  numerous  foramina.  Near  the  junctions  of  the 
roots  of  the  arches  and  the  body  (along  the  superior  and  inferior 
margins)  there  are  four  costal  facets  (fovea  costales)  two  superior  and 
two  inferior.  In  two  successive  vertebrae  the  contiguous  facets 
accommodate  the  head  of  a  rib. 

The  roots  of  the  vertebral  arches  slope  upward  and  backward  so  that 
the  superior  intervertebral  notch  is  slight  and  the  inferior  notch  is 
deep.  The  laminae  are  flat  and  broad  and  slope  downward  and  out- 
ward, thus  overlapping  those  of  the  vertebra  below.  The  vertebral 
foramen  is  circular  and  smallest  in  this  portion  of  the  vertebral 
column  as  this  portion  of  the  spinal  cord  is  smallest  in  diameter. 
The  spinous  processes  vary;  in  the  upper  part  of  the  thoracic  region 
they  are  short  and  nearly  horizontal,  while  in  the  lower  part  they  are 


VERTEBRAL    COLUMN  20. 

longer,  heavier  and  successively  more  oblique.  Each  may  possess  a 
tubercle  at  its  extremity. 

The  transverse  processes  are  larger  in  the  upper  thoracic  vertebra? 
and  gradually  decrease  in  length.  They  are  directed  laterally  and 
dorsallv.  Near  the  extremity  of  each  there  is  a  concave  facet  for 
articulation  with  the  tubercle  of  the  rib. 

The  superior  articular  facets  are  nearly  vertical,  facing  dorsallv 
and  a  little  laterally.  The  inferior  facets  are  directed  downward 
and  face  ventrally  and  a  little  medially. 

The  first  thoracic  vertebra  resembles,  somewhat,  a  cervical  verte- 
bra.    The  superior  costal  facet  is  more  on  the  side  of  the  body;  the 


Inferior  facet  for.head  of  rib 


) 


Spinous  process 
Fir,.  o. — The  sixth  thoracic  vertebra  from  the  side.     (Sobotta  and  McMurrich.) 

transverse  processes  are  quite  long  and  the  superior  intervertebral 
notches  are  well  marked.  The  superior  articular  facets  are  more 
sloping  and  are  directed  upward  and  dorsallv. 

The  ninth  thoracic  vertebra  has  usually  no  inferior  costal  facets. 

The  tenth  thoracic  vertebra  has  only  a  superior  costal  facet  and  the 
facet  upon  the  transverse  process  is  small  or  absent. 

The  eleventh  thoracic  vertebra  has  one  costal  facet  below  the 
superior  margin  and  none  upon  the  short  transverse  process. 

The  twelfth  thoracic  vertebra  has  one  costal  facet  upon  the  root 
of  the  vertebral  arch.  The  transverse  process  is  thick  and  presents 
a  number  of  tubercles  resembling  those  of  the  lumbar  vertebrae. 
Its  inferior  articular  processes  face  laterallv. 

THE  LUMBAR  VERTEBRA  (VERTEBRAE  LUMBALES) 

The  lumbar  vertebrae  are  the  largest  of  the  true  vertebrae  and  are 
five  in  number. 

The  body  is  reniform  and  the  ventrodorsal  dimension  is  about 
half  the  transverse  dimension.  The  superior  and  inferior  surfaces 
are  smooth  and  somewhat  concave  and  rimmed.     The  ventral  and 


3° 


OSTEOLOGY 


lateral  surfaces  are  quite  concave  from  above  downward  and  show 
numerous  foramina.  The  dorsal  surface  is  concave  from  side  to  side 
as  well  as  from  above  downward.  The  body  is  slightly  thicker 
behind  than  in  front  giving  a  curve  to  this  part  of  the  column,  with 
the  convexity  forward.  The  roots  of  the  vertebral  arches  are  directed 
dorsally  and  are  short  and  thick.  Both  intervertebral  notches  are 
well  marked.  The  laminas  are  broad  and  nearly  vertical.  The 
vertebral  foramen  is  large  and  triangular.  The  spinous  process  is 
short,  flat  and  broad;  each  is  directed  dorsally  and  slightly  down- 
ward. The  transverse  processes  are  somewhat  slender  and  are  directed 
laterally  and  horizontally.     In  the  successive  vertebra?  the  lamina? 


Superior  articular  process 


Transverse  process 


Fig.   io. — The  third  lumbar  vertebra  seen  from  above.      (Sobotta  and  McMurrich.) 

arise  at  a  more  ventral  level  from  the  roots  of  the  vertebral  arches. 
They  apparently  represent  the  costal  elements  of  the  thoracic  ver- 
tebrae. Upon  the  dorsal  surface  of  each  transverse  process  are  the 
accessory  tubercles.  The  superior  articular  processes  are  oval  and  lie 
at  the  junction  of  the  roots  of  the  arches  and  the  lamina.  The 
articular  facets  are  concave,  vertical  and  face  medially.  The  inferior 
articular  processes  are  at  the  inferior  margin  of  each  lamina  at  the 
root  of  the  spinous  process.  The  oval  and  nearly  flat  facets  face 
laterally.  These  processes  are  nearer  the  median  plane  than  are 
the  superior  ones  and  so  are  overlapped  by  these  when  articulated. 
The  fifth  lumbar  vertebra  has  the  largest  body.  Its  ventral 
vertical  dimension  is  much  greater  than  the  dorsal  vertical  measure- 
ment and  so  assists  the  sacrum  in  forming  the  sacrovertebral  angle. 
The  transverse  processes  are  pyramidal  in  shape  and  arise  from  the 
sides  of  the  body  and  the  vertebral  arches.  The  superior  articular 
facets  are  directed  more  dorsally  than  medially.  The  inferior  facets 
face  ventrally  and  laterally  and  are  in  a  line  with  the  superior  pro- 
cesses.    The  spinous  process  is  short  and  narrow. 


THE    SACRUM  3 1 

Ossification. — The  vertebra  are  of  endochondral  origin  and  each  develops 
irom  four  primary  (two  for  the  lamina  and  two  for  the  body)  and  three  secondary 
centers,  usually.  The  centers  for  the  lamina  appears  during  the  sixth  week  of 
fetal  life  and  spread  into  the  base  of  the  spinous  process,  the  roots  of  the  arches 
and  the  transverse  processes.  The  centers  for  the  body  appear  during  the 
eighth  week  and  these  centers  soon  fuse.  At  birth  the  vertebra  consists  of  three 
parts.  During  the  first  year  the  laminae  fuse  dorsally  (in  the  lumbar  region 
first  and  then  upward)  and  during  the  third  year  the  body  and  laminae  fuse. 
The  secondary  centers  appear  at  about  the  sixteenth  year.  There  is  one  for  the 
tip  of  each  transverse  process  and  one  for  the  tip  of  the  spinous  process.  All  parts 
are  fused  into  one  mass  by  the  twenty-fifth  to  the  thirtieth  years. 

The  number  of  centers  for  the  atlas  is  variable  (two  to  five).  Usually  three 
centers  appear,  one  for  each  lateral  mass  (sixth  week  of  fetal  fife)  and  one  for  the 
ventral  arch  (end  of  the  first  year). 

The  epistropheus  is  usually  developed  iromfive  or  six  primary  and  two  secondary 
centers.  The  primary  centers  are  one  for  each  lamina  (seventh  to  eighth  week), 
one  (or  two)  for  the  body  (fourth  month)  and  two  for  the  dens  (sixth  month). 
During  the  second  year  a  secondary  center  appears  for  the  apex  of  the  dens  and 
this  unites  with  the  main  mass  at  about  the  twelfth  year.  The  oilier  center  is 
for  a  thin  epiphyseal  disc  on  the  inferior  surface  of  the  body. 

THE  FIXED  OR  FALSE  VERTEBRjE 

The  sacrum  represents  the  fusion  of  five  vertebrae.  It  is  said  to  be 
roughly  triangular  in  shape  (better  like  a  curved  wedge).  Its  ventral 
or  pelvic  surface  is  smooth,  concave  from  side  to  side  as  well  as  from 
above  downward.  It  presents  four  transverse  ridges  that  terminate 
at  the  ventral  sacral  foramina.  These  foramina  extend  laterally  as 
shallow  grooves  and  dorsally  they  communicate  with  the  vertebral 
canal.  That  portion  on  each  side  lateral  to  the  foramina  constitutes 
the  lateral  mass  (pars  lateralis).  Its  lateral  surface  (upper  part)  is 
large  and  ear-shaped  (articular  surface)  and  articulates  with  the  os 
innominatum  on  each  side.  Dorsal  to  this  area  is  the  sacral  tuber- 
osity. The  superior  surface  articulates  with  the  fifth  lumbar  verte- 
bra; it  resembles  that  vertebra  in  this  part  and  possesses  superior 
articular  processes. 

The  dorsal  surface  is  rough,  convex  from  above  downward  and 
shows  a  median  as  well  as  two  pairs  of  lateral  ridges  and  four  pairs  of 
dorsal  sacral  foramina.  The  crest  (crista  sacralis  media)  is  in  the 
midline  and  consists  of  the  spinous  processes  of  the  upper  four  sacral 
vertebra;.  The  fifth  spinous  process  is  absent  and  the  lamina;  sepa- 
rated so  that  the  vertebral  canal  is  exposed.  This  gap  is  the  hiatus 
sacralis.  Lateral  to  the  crest  is  the  sacral  groove  on  each  side.  This 
groove  is  bounded  laterally  by  a  crista  sacralis  articularis,  which  is 
formed  by  the  row  of  fused  articular  processes.  Lateral  to  each 
crest  is  a  row  of  dorsal  sacral  foramina  through  which  pass  the  dorsal 
branches  of  the  sacral  spinal  nerves.  Lateral  to  the  foramina  is  a 
row  of  tubercles  forming  the  lateral  ridge  (crista  sacralis  lateralis)  of 
each  side.     This   represents   the   transverse  processes  of   the  true 


32 


OSTEOLOGY 


Superior  articular  iirja-a 


Fig.   ii. — The   sacrum   seen   fr 


\ 

Apex  of  sacrum 

front    (pelvic  surface).     (Sobotta   and    McMurrich.) 


Superior  articular  process  Sacral  canal 


FlG.    12. — The  sacrum  seen  from  behind  (dorsal  surface).      (Sobotta  ami  McMurrich.) 


THE    COCCYX  33 

vertebrae.  The  sacral  cornua  are  the  downward-projecting  inferior 
articular  processes  of  the  last  sacral  vertebra.  The  apex  of  the 
sacrum  represents  the  oval  body  of  the  fifth  sacral  vertebra. 

The  sacral  canal  is  flattened  dorsoventrally  and  curves  with  the 
bone.     It  communicates  with  the  dorsal  and  ventral  sacral  foramina. 

The  sacrum  of  the.  female  is  shorter,  broader  and  less  curved  than 
in  the  male.     In  the  male  it  is  directed  more  obliquely  backward. 

Ossification. — The  sacrum  has  thirty-five  centers  of  ossification.  The  body 
of  each  segment  has  three  centers,  each  arch  two,  the  lateral  mass  has  six  (two  for 
each  of  the  first  three  segments)  and  each  of  the  lateral  surfaces  has  two  centers. 
The  first  centers  appear  during  the  eighth  or  ninth  week  of  fetal  life  and  all  are 
fused  between  the  twenty-fifth  and  thirtieth  years. 

Muscles  Attached. — To  the  ventral  surface  the  mm.  pyriformis,  the  coccygeus 
and  part  of  the  iliacus.  To  the  dorsal  surface  the  mm.  gluteus  maximus,  the 
latissimus  dorsi.  sacrospinalis  and  multifidus. 

THE  COCCYX  (OS  COCCYGIS) 

The  coccyx  represents  the  fusion  of  four  rudimentary  vertebrae. 
The  first  segment  is  the  largest  and  the  others  are  successively  smaller. 
The  superior  surface  of  the  first  segment  shows  an  oval  concave  facet 


First  coccygeal  vertebra 
Second  coccygeal  vertebra 


Fig.   13. — The  coccyx  seen  from  in  front.      (Sobotta  and  McMurrich.) 

that  articulates  with  the  sacrum.  The  dorsal  surface  presents  two 
upward-projecting  processes  [cornua  coccygea)  representing  articular 
processes  for  articulation  with  the  cornua  sacralis.  These  assist  in 
forming  two  foramina  for  the  fifth  pair  of  sacral  nerves.  Laterally 
this  segment  presents  a  rudimentary  transverse  process  on  each  side. 
The  second  may  also  present  such  processes  but  the  remaining  seg- 
ments are  rudimentary  nodules  of  bone. 

Ossification. —  The  coccyx  is  developed  from  four  centers,  one  for  each  segment. 
That  for  the  first  segment  appears  during  the  first  to  the  fourth  years,  the 
second,  from  the  fifth  to  the  tenth  years,  the  third,  from  the  tenth  to  the  fifteenth 
and  the  fourth,  from  the  fourteenth  to  the  twentieth  years.  The  fusion  of  the 
parts  is  complete  about  the  thirtieth  year. 

Muscles  Attached. — To  the  dorsal  surface  the  m.  gluteus  maximus;  to  the 
lateral  margin  the  mm.  coccygeus  and  levator  ani  on  each  side;  to  the  tip  the 
m.  sphincter  ani  externus. 


34 


OSTEOLOGY 


THE  VERTEBRAL  COLUMN  AS  A  WHOLE 

When  the  vertebrae  are  articulated  a  peculiarly  curved,  and  for 
the  most  part  movable,  column  is  formed.  The  adult  vertebral 
column  averages  from  27J-2  inches  to 
28%  inches  (70  to  73  cm.)  in  length, 
in  the  male,  and  in  the  female  about 
23%  inches  (60  cm.).  The  individual 
parts  in  the  male  are  as  follows:  cervical, 
13  to  14cm.;  thoracic  27  to  29  cm.; 
lumbar,  17  to  18  cm.;  sacrococcygeal, 
12  to  15  cm. 

The  ventral  part  consists  of  the  bodies 
of  the  vertebrae  that  serve  as  a  support 
for  the  head  and  trunk.  The  verte- 
bral arches  and  laminae  form  the  ver- 
tebral canal  that  contains  the  spinal 
cord  and  its  membranes.  This  canal 
is  largest  in  the  cervical  and  lumbar 
regions  and  is  open  at  the  last  sacral 
segment.  At  the  side  of  the  column 
the  intervertebral  notches  now  form  the 
intervertebral  foramina  through  which 
the  roots  of  the  spinal  nerves  pass. 
The  first  two  cervical  foramina  are 
dorsal  to  the  articular  processes  and 
the  remainder  (as  far  as  the  sacrum) 
are  ventral  to  these  processes.  Dor- 
sally  the  spinous  processes  produce  a 
dorsal  median  ridge  and  the  transverse 
processes  a  lateral  ridge,  on  each  side. 
As  a  result  a  groove  is  formed  on  each 
side  of  the  median  ridge  called  the  ver- 
tebral grooves  and  these  are  occupied  by 
the  muscle  that  operate  the  vertebral 
column. 

Curves  are  also  noted.  When  viewed 
from  the  ventral  surface  the  vertebral 
column  may  have  a  slight  lateral  curve 
in  the  thoracic  region  with  the  con- 
vexity to  the  right;  this  is  due,  prob- 
ably, to  the  greater  use  of  the  right  side 
and  right  upper  extremity  or  by  pressure 
exerted  by  the  thoracic  aorta  upon  the  thoracic  vertebrae.  Viewed 
from  the  side  the  vertebral  column  presents  four  dorsoventral  curves, 


Fig.   14. — The    vertebral  colu 
seen  from    the    left   side.     (Sobolta 
and  UcMurrich.) 


THE    STERNUM  35 

cervical,  thoracic,  lumbar  and  sacral.  The  thoracic  and  sacral  are 
primary  curves,  existing  during  fetal  life,  while  the  other  two  are 
acquired  curves;  they  are  formed  after  the  child  begins  to  walk.  The 
cervical  curve  is  slight  and  has  its  convexity  ventral;  the  thoracic 
curve  is  marked  and  its  concavity  is  ventrally  directed.  The  lower 
part  of  this  curve  becomes  continuous  with  the  lumbar  curve  which 
is  also  marked  and  has  its  convexity  ventrally  directed.  The  sacral 
curve  has  its  concavity  ventrally  directed  and  from  its  length  is  the 
deepest  and  most  marked  curve.  The  sudden  dorsal  curve  of  the 
first  segment  of  the  sacrum  causes  the  fifth  lumbar  vertebra  to  form 
a  prominent  projection  called  the  sacrovertebral  angle. 

THE  STERNUM 

The  sternum  constitutes  the  middle  portion  of  the  ventral  bound- 
ary of  the  thorax  and  is  a  fairly  long,  flat  and  thin  bone;  it  is  pointed 
at  its  inferior  extremity,  constricted  near  its  middle  and  consists  of 
three  parts,  the  manubrium,  body  and  xyphoid  process. 

The  manubrium,  or  handle,  is  the  superior  portion  and  its  ventral 
surface  is  smooth  and  somewhat  saddle-shaped.  To  it  are  attached 
the  mm.  pectoralis  major  and  sternomastoideus.  Its  superior  margin 
is  thickened  and  uneven  exhibiting  a  median  notch,  the  suprasternal 
notch,  or  incisura  jugularis,  that  is  more  pronounced  when  the  clav- 
icles are  in  position.  On  each  side  of  this  notch  there  is  an  oblique 
facet  for  articulation  with  the  clavicle,  the  incisura  clavicularis. 
Just  inferior  to  this  another  facet  is  noted,  on  the  lateral  margin, 
for  articulation  with  the  cartilage  of  the  first  rib.  Inferior  to  this 
the  bone  becomes  narrower.and  the  inferior  corner  is  absent,  forming 
a  facet  with  a  like  area  upon  the  next  portion  of  the  sternum,  for 
the  second  costal  cartilage.  The  inferior  margin  of  the  manubrium 
is  connected  with  the  second  segment  by  cartilage  or  it  may  be  fused 
with  it.  The  dorsal  surface  is  smooth  and  slightly  concave  and  shows 
numerous  foramina.  It  affords  attachment  to  the  mm.  sterno- 
hyoideus  and  sternothyroideus. 

The  body  (corpus  sterni)  is  the  middle  and  longest  segment.  It  is 
nearly  flat  from  side  to  side  and  convex  from  above  downward. 
Its  superior  portion  is  narrower  than  the  inferior  part.  The  ventral 
surface  (planum  sternale)  is  smooth  but  shows  three  more  or  less 
marked  transverse  ridges  that  indicate  the  four  segments  that  fuse 
to  form  this  portion  of  the  sternum.  It  affords  attachments  to  the 
m.  pectoralis  major  upon  each  side.  The  superior  margin  is  attached 
or  fused  to  the  manubrium  forming  an  angle  at  the  junction  that  is 
usually  appreciable  to  the  touch.  This  is  the  sternal  angle  (angulus 
sterni).  The  lateral  portions  of  this  margin  complete  the  facet  for 
the  second  costal  cartilage.     The  inferior  margin  is  convex  and  its 


3° 


OSTEOLOGY 


middle  part  is  connected  to  the  xyphoxd  process.  Latera  to  th 
the  sixth  and  seventh  costal  cartilages  are  attached.  Each  lateral 
margin  is  thick  and  irregular  presenting  facets  at  the  extremities 
of  the  ridges  that  accommodate  the  third,  fourth  and  fifth  costal 
cartilages  The  dorsal  surface  is  concave  from  above  downward  and 
may  exhibit  the  transverse  ridges.  Its  superior  portion  affords 
attachment  to  the  m.  transversus  thoracis,  or  triangularis  sterm, 
while  the  remainder  is  in  relation  with  the  pericardium  and  pleura. 
The  xvPlwid  process  (processus  xyphoideus)  is  the  smallest  segment 
and  variable  in  form.     Its  base  is  attached  to  the  body  of  the  sternum 


Jugular  notch 

Clavicular 

notch       "                -^ x 

■ 

first  rib           I 

Manubrium 

Notch  for           >—  -^yar 
second  rib           -  ^Bi iiJx. 

Notch  for  _ ).£'. 

third  rib                                     V 

{ 

Notch   for 

fourth  rib         .'«g                    \ 

Body  of  sternum 

>  - 

Notch  for EM                 / 

fifth  rib 

Notch  for lSjC"'          g 

sixth  rib               ^W^     k     1 

Notch  for                      yvS 

seventh  'rib             '  jPIrl 

Xiphoid  process 


Fic.   IS— The  sternum  seer,  from  in  front.      'SoboUa  and  McMurrich.) 

while  its  apex  affords  attachment  to  the  linea  alba  of  the  abdomen. 
The  process  slopes  dorsally  forming  the  pit  of  the  stomach,  or  ,n,r- 
sterZl  depression.  To  its  lateral  margins  the  aponeuroses  o  the 
abdominal  muscles  are  attached,  while  the  dorsal  surface .afford,  at- 
tachment to  a  portion  of  the  m.  transversus  thoracis  and  diaphragm. 

In  the  male  the  sternum  is  longer  and  broader  than  m  the  female 
its  direction  is  more  oblique  and  variations  of  the  different  segments 
are  also  noted. 

Ossification  -The  sternum  is  an  endochondral  bone  and  the  cartilaginous 
stem  mf  formed  bv  the  fusion  of  two  lateral  bars.  Ossification  begms  dunng 
™h  month  of  fetal  life  with  the  appearance  of  the  center  for  the  manubrium. 


THE    RIBS  37 

Secondary  centers  may  appear  for  the  clavicular  facets.  The  body  develops 
from  four  single,  or  double  centers  (one  for  each  segment)  and  their  appearance 
usually  follows  that  for  the  manubrium;  the  last  one  appears  just  before  birth. 
One  center  appears  for  the  xyphoid  process  during  the  third  year.  The  seg- 
ments of  the  body  fuse  between  early  childhood  and  the  twentieth  to  the  twenty- 
fifth  years.  The  manubrium  and  body  may  never  fuse  while  the  body  and 
xyphoid  process  fuse  at  about  the  fortieth  to  fiftieth  years. 

Muscles  Attached. — The  mm.  pectoralis  major,  sternohyoidens,  sternothy- 
roideus,  transversus  thoracis  the  diaphragm  and  the  aponeuroses  of  the  mm. 
obliquus  internus  abdominis,  obliquus  externus  abdominis  and  transversalis 
abdominis — nine  pairs. 

THE  WBS  (COSTE) 

The  ribs,  or  hemal  arches,  twelve  in  number  on  each  side,  form  a 
bony  protection  for  the  thoracic  contents.  They  are  movable  as 
they  articulate  with  the  thoracic  vertebrae,  dorsallv,  and  with  the 
costal  cartilages,  ventrally;  by  means  of  the  latter  they  are  connected 
with  the  sternum.  The  first  seven  constitute  the  true  ribs  [costm 
vera)  as  their  cartilages  articulate  individually  with  the  sternum. 
The  remainder  are  called  false  ribs  (costm  spuria);  of  these  the  carti- 
lages of  the  eighth,  ninth  and  tenth  ribs  join  that  of  the  seventh  rib 
[vertebrochondral  ribs)  while  the  costal  cartilages  of  the  eleventh  and 
twelfth  ribs  are  free  at  their  ventral  extremities  [floating  ribs). 

A  typical  rib  presents  a  head,  neck,  tubercle,  shaft  and  angle.  The 
head  (capitullum  costae)  is  slightly  enlarged  and  represents  the  dorsal 
or  vertebral  extremity  of  the  rib.  Its  medial  surface  has  an  articular 
facet  divided  by  a  ridge  [crista  capituli)  into  a  larger  inferior  portion 
that  rests  in  the  superior  facet  of  the  body  of  a  thoracic  vertebras 
(from  which  it  takes  its  number) ;  the  smaller  superior  facet  articu- 
lates with  the  inferior  facet  of  the  body  above.  -To  the  crista  is 
attached  the  interarticular  ligament.  The  neck  (collum)  is  a  nar- 
row part  of  the  rib  connecting  the  head  to  the  shaft  and  here  a 
tubercle  is  seen  dorsally.  The  ventral  surface  of  the  neck  is  smooth 
and  the  dorsal  surface  roughened  for  the  attachment  of  the  ligaments 
of  the  neck.  The  superior  margin  may  present  a  ridge  for  the  attach- 
ment of  the  ventral  costotransverse  ligament.  The  inferior  margin 
is  smooth  and  continuous  with  the  costal  groove. 

The  tubercle  is  on  the  dorsal  surface  of  the  rib  at  the  junction  of 
the  neck  and  shaft.  It  presents  an  oval  articular  portion  that  faces 
inferiorly  and  dorsally.  It  articulates  with  the  facet  on  the  trans- 
verse process  of  a  thoracic  vertebra.  The  nonarticular  portion 
affords  attachment  to  the  fibers  of  the  ligament  of  the  tubercle.  A 
groove,  occupied  by  the  lateral  division  of  the  dorsal  branch  of  a 
thoracic  spinal  nerve,  separates  tubercle  from  shaft  and  neck. 

The  shaft  is  thin,  curved  and  band-like.  It  varies  in  length  in  the 
different  ribs.     The  seventh  and  eighth  are  the  longest  and  the  first 


3§ 


OSTEOLOGY 


the  shortest.  The  curvature  is  not  uniform  but  varies  in  the  different 
regions  and  gives  the  peculiar  shape  of  the  thorax.  From  the  tuber- 
cle the  rib  proceed  first  laterally  and  at  a  variable  distance  in  the 
different  ribs,  then  it  turns  rather  sharply  in  a  ventral  direction. 
This  change  of  direction  produces  the  angle  (angulus  costa).  The 
distance  from  tubercle  to  angle  is  greater  in  the  eighth  rib  and  nil  in 
the  first  rib.  The  rib  is  also  twisted  so  that  the  ventral  end  is  at  a 
lower  level  than  the  head,  when  the  rib  is  placed  upon  a  plane  surface. 
This  is  most  noticable  in  the  seventh  and  eight  ribs  and  least  in  the 
first  and  last  ribs. 

The  shaft  is  flattened  and  has  two  surfaces,  lateral  and  medial. 
The  lateral  surface  is  smooth  and  convex  and  faces  according  to  the 
part  of  the  thorax  in  which  it  is  placed,  i.e. ,  superiorly  in  the  upper  part, 
laterally  in  the  middle  of  the  thorax  and  slightly  downward  in  the 
lower  part.     The  medial  surface  is  smooth  and  faces  in  the  opposite 


Fig.   i  6.— The 


nth  rib  of  the  left 


from  within.      (Sobolta  and  McMurrich.) 


direction.  The  superior  margin  is  thick  and  rounded  and  affords 
attachments  to  the  mm.  intercostales  externus  et  internus.  The 
inferior  margin  is  sharp  and  dorsally  it  is  grooved;  here  it  forms  the 
costal  groove  {sulcus  costalis)  which  disappears  ventrally.  The  in- 
ferior margin,  between  the  angle  and  the  tubercle,  is  ridged  and 
affords  attachment  to  the  m.  iliocostalis.  The  costal  groove  contains 
the  intercostal  vessels  and  the  lip  affords  attachment  to  the  external 
and  internal  intercostal  muscles.  In  the  groove  are  seen  the  nutrient 
foramina  that  are  directed  toward  the  vertebral  extremity. 

Peculiar  Ribs. — The  first  rib  is  the  smallest.  The  head  is  small 
and  the  head  articulates  with  only  one  vertebral  body,  the  first.  The 
neck  is  short  and  flattened  from  above  downward.  The  tubercle, 
at  the  junction  of  the  neck  and  shaft,  is  prominent  and  bears  a  small 
facet,  on  its  under  surface,  for  articulation  with  the  transverse  process 
of  the  first  thoracic  vertebra.  The  angle  and  tubercle  are  coincident. 
The  medial  margin  is  thin  and  presents,  near  its  middle,  the  tubercu- 
lum  scaleni;  this  margin  affords  attachment  to  Sibson's  fascia.  The 
superior  surface  is  uneven  and  at  the  tubercle  area  a  ridge  passes  ven-. 
trally  and  laterally  separating  two  grooves;  the  ventral,  deeper,  one 
is  for  the  subclavian  vein,  while  the  dorsal  one  is  for  the  subclavian 


THE    COSTAL   CARTILAGES 


39 


artery  and  ventral  division  of  the  first  thoracic  nerve  (sulcus  sub- 
clavian). Dorsal  to  the  latter  groove  the  surface  is  roughed  for  the 
attachment  of  the  m.  scalenius  medius.  The  inferior  surface  is 
smooth  and  covered  with  pleura.  The  lateral  margin  is  thickened 
and  rough  dorsally  for  attachment  of  the  first  digitation  of  the  m. 
serratus  anterior. 

In  the  second  rib  there  is  no  twist  and  the  surfaces  are  turned  so 
that  they  are  obliquely  directed.  The  head  presents  two  facets  and 
the  angle  is  distinct  from  the  tubercle.  The  lateral  surface  presents 
a  roughened  area  for  the  attachment  of  part  of  the  first  and  the  entire 
second  digitation  of  the  m.  serratus  anterior.  The  margin  likewise 
affords  attachment  to  the  external  and  internal  intercostal  muscles. 

On  the  tenth  rib  there  is  only  one  facet  on  the  head  and  usually 
none  on  the  tubercle. 


Fig.  17. — The  first  ri 
and  McMurrich.) 

Fig.  18. — The  second 
and  McMurrich.) 


Tubers- 
Tubercle 

b  of   the  right  side  seen  from  above  and  from  the  side.      (Sobotta 
rib  of  the  right  side  seen  from  above  and  from  the  side.      (Sobotta 


On  the  eleventh  and  twelfth  ribs  the  heads  show  only  one  facet;  the 
tubercles  and  angles  are  faint.  The  ventral  ends  are  pointed  and 
tipped  with  cartilage.     Both  ribs  are  short. 

Ossification. — The  ribs  are  of  endochondral  origin  and  each  rib  is  developed 
from  three  centers,  except  the  last  two  pairs.  The  center  for  the  shaft  appears 
during  the  ninth  or  tenth  week  of  fetal  life.  The  centers  for  the  head  and  the 
tubercle  appear  about  the  sixteenth  to  the  twentieth  years.  Fusion  is  complete 
about  the  twenty-fifth  year.  The  last  two  ribs  have  tuv  centers  each,  one  for 
the  shaft  and  one  for  the  head. 

Muscles  Attached. — The  mm.  intercostales  interna  et  externi,  scalenus  an- 
terior, scalenus  medius.  scalenus  posterior,  pectoralis  minor,  serratus  anterior, 
latissimus  dorsi,  diaphragma,  quadratus  lumborum,  obliquus  externus  ab- 
dominis, serratus  posterior  superior,  serratus  posterior  inferior,  iliocostalis  lum- 
borum, iliocostalis  dorsi,  iliocostalis  cervicis,  longissimus,  levatores  costorum 
and  infracostales  (nineteen). 

THE  COSTAL  CARTILAGES 

The  costal  cartilages  are  the  bars  of  cartilage  attached  to  the  ribs, 
on  the  one  hand,  and  on  the  other  directly  or  indirectly  to  the 


}o 


OSTEOLOGY 


sternum,  except  the  eleventh  and  twelfth  pairs.  The  first  seven  pairs 
articulate  with  the  sternum  at  the  designated  notches  and  usually  a 
synovial  membrane  exists  at  the  joints.  The  eighth,  joined  by  the 
ninth  and  tenth  cartilages,  on  each  side,  is  attached  to  the  seventh 
cartilage.  The  eleventh  and  twelfth  are  small  and  merely  tip  these 
ribs.  The  cartilages  increase  in  length  from  the  first  to  the  seventh 
and  then  again  shorten.  Their  direction  and  obliquity  vary  as  can 
be  noted  in  the  illustration. 

THE  THORAX  AS  A  WHOLE 


The  thorax  or  chest  consists  of  a  framework  of  bones  and  cartilages. 
Between  the  ribs  lie  the  intercostal  muscles  and  membranes  com- 


Fig.   19. — Ventral 


pletely  closing  these  intervals.  The  thorax  has  the  shape  of  a  trun- 
cated cone,  flattened  from  before  backward,  shorter  in  front  than 
behind.  It  presents  four  walls,  or  boundaries,  dorsal,  two  lateral  and 
ventral ;  it  has  two  apertures,  superior  and  inferior. 

The  dorsal  wall  consists  of  the  twelve  thoracic  vertebra;  and  the 


THE    FRONTAL    BONE  41 

ribs  to  their  angles.  On  each  side  of  the  midline  is  seen  a  deep  groove, 
the  vertebral  groove.  The  bodies  of  the  vertebra?  project  into  the 
cavity  of  the  thorax  and  reduce  its  dorsoventral  dimension  markedly. 
The  lateral  walls  consist  of  the  shafts  of  the  ribs.  The  ventral  wall 
consists  of  the  sternum  and  the  costal  cartilages.  This  wall  is  the 
shortest  and  slopes  downward  and  forward. 

The  superior,  or  cephalic  aperture,  is  kidney-shaped,  about  4  inches 
(10  cm.)  from  side  to  side  and  about  2  inches  (5  cm.)  dorsoventrally. 
Its  boundaries  are  as  follows:  dorsally,  the  body  of  the  first  thoracic 
vertebra;  laterally,  the  first  ribs;  vent  rally,  the  upper  margin  of  the 
sternum.  This  aperture  slopes  downward  and  forward  so  that  its 
ventral  margin  is  on  a  level  with  lower  border  of  the  body  of  the 
second  thoracic  vertebra,  in  the  male,  and  in  the  female  at  the  lower 
border  of  the  third  thoracic  vertebra.  The  main  structures  trans- 
mitted are  the  esophagus,  trachea,  thoracic  duct,  the  innominate, 
left  common  carotid  and  left  subclavian  arteries,  the  right  and  left 
innominate  veins,  the  vagal,  phrenic  and  sympathetic  nerves  and  the 
apex  of  each  lung  covered  by  the  cervical  extension  of  the  parietal 
pleura. 

The  inferior,  or  caudal  aperture  is  not  a  true  aperture  as  it  is  closed 
in  by  the  diaphragm.  Its  boundaries  are  as  follows:  dorsally  the 
body  of  the  twelfth  thoracic  vertebra;  laterally  the  twelfth  ribs; 
ventrally  the  eleventh,  tenth,  ninth,  eighth  and  seventh  costal  carti- 
lages. These  joined  cartilages  sloping  upward  and  inward  form  with 
their  fellows  of  the  opposite  side  the  subcostal  angle  at  the  midline. 

The  thorax  is  widest  at  the  level  of  the  eight  or  ninth  ribs,  deeper 
behind  than  in  front  and  deeper  on  the  left  than  on  the  right  side. 
In  the  female  the  capacity  is  less,  the  ribs  more  movable,  the  inlet  has 
a  greater  slant  and  the  sternum  is  shorter  than  in  the  male.  Upon 
transverse  section  the  thorax  is  kidney-shaped. 

THE  BONES  OF  THE  SKULL  (OSSA  CRANII) 

This  portion  of  the  skeleton,  comprising  the  entire  head,  is  made 
up  of  twenty-two  bones;  it  is  divided  into  cranium  cerebrate  and 
cranium  viscerate.  The  cranium  cerebrale  consists  of  fifteen  bones, 
the  occipital,  sphenoid,  ethmoid,  frontal,  parietal  (two),  temporal 
(two),  inferior  nasal  conchas  (two),  lacrimal  (two),  nasal  (two),  and 
vomer.  The  cranium  viscerale  consists  of  the  ossa  faciei  which  are 
the  mandible,  maxillae  (two),  zygomatic  (two),  palatal  bones  (two). 
The  hyoid  bone  will  be  described  in  this  section. 

THE   FRONTAL   BONE    (OS   FRONTALE) 

The  frontal  bone  constitutes  the  front  part  of  the  cerebral  cranium 
and  consists  of  frontal,  orbital  and  nasal  portions. 


OSTEOLOGY 

and  convex  ventrally.     Upon   ea  h    -ronta,  luberosity.     The 

marked  part  of  the  convex^onsntute,       £       ^  ^  ^ 

tyertor  HMrxM  presents  an  arch  on m  ^supraorbital 

b>'  r  Ted  rStSSSX^  Processesf  laterally 
„„/(•/;  or  A"*"™.     Each  arch  i si  o         .  ]ls  arches  upward 

is  the  zygomatic  process  from  which  the hm  at  mpo  _ 

and  backward  upon  the  temporal  portion  of  the  bone  <g  £ 

dfa).     This  surface  is  smooth  and  ~ncave  and  conrtr  ut-      P 
of  the  temporal  fossa  and  here  the  «^?S2iSS  articulates 
the  arch  is  bounded  by  the  ««feri  ^f^^X  processes  lies 
with  the  nasal  bone.     Between  the  two  -ed.aUngular^ 

Frontal  eminence 


Supercilt 


arch 

Nasal  portion        Frontal  spine 
Fig.   20.— The  frontal  bone  seen  from  in  front. 


Zygomatic 
'process 
Supraorbital  margin 
Supraorbital  notch 
(Snbotta  awi  McMurriM 


From  this  the  supcrcilhary  arch  {anus  stipercunan* , 

S   -   o^tal  portion  £ars   orb i^compri ^  — L 
arched  part  on  each    ^  f  the  m  ^ Jn  Q^A  and  sepa 

ra^t^t^ 

to  this  is  the  nasal  notch  from  ^."^^Satea  with  the 
projects  downward  as  the    rontal  #g  **ef™*n  each  side 
(two)  nasal  and  ethmoidal  bones.     %^*Jf  ^      Jusl  wlthin 
of  the  nasal  process  constitutes  the  roof  of  a  nasal a   a 
the  medial  part  of  the  orbital  margin  ,,  the  ^ ^       £   .      J 

(g r  *  ^  ''^  thl"  ^        utt  w!^  th^Lal  part  of  the 
obliquus  superior  of  the  eyeoan.     j  u 


THE    PARIETAL   BONES 


43 


orbital  margin  is  the  lacrimal  fossa  for  the  lacrimal  gland  (fossa 
glandule  lacrimalis). 

The  cerebral  surface  is  concave  and  accommodates  the  frontal 
lobes  of  the  cerebrum.  It  is  smooth  but  uneven  due  to  the  pressure 
of  the  meningeal  vessels  and  the  gyri  of  the  frontal  lobes.  From 
the  center  of  the  upper  margin  a  groove  {sulcus  sagittalis)  descends 
and  terminates  in  a  crest  at  the  end  of  which  is  the  foramen  cecum. 
Here  the  superior  sagittal  sinus  begins. 

Articulations. — Dorsally,  with  the  parietals  and  sphenoid;  laterally,  with  the 
zygomatic  bones;  inferiorly  and  medially,  with  the  nasals,  maxilla;,  lacrimals  and 
ethmoid  bones. 

Sagittal  groove 


Cerebral 
surface  of 
frontal 
portion 


Cerebral  surface  (of  orbital  portion) 

Foramen  i 


Fig.  21. — The  frontal  bone  seen  from  behind  (ce 


^? 

Zygomatic 
process 

Frontal  crest 

Orifice  of  frontal  sinus 
•Frontal  spine 

bral  surface).      {Sobotta  t 

nd  XlcMurrich.) 

Ossification. —  Tuv  lateral  primary  centers  and  three  pairs  of  secondary  centers. 
The  primary  centers  appear  about  the  sixth  or  seventh  week  of  fetal  life  and 
form  the  bulk  of  the  bone.  The  secondary  centers  appear  later,  one  pair  for  the 
frontal  spine,  one  center  for  each  zygomatic  process  and  a  center  on  each  side 
at  the  region  of  the  trochlear  pit.  These  centers  fuse  on  each  side  by  the  sixth 
or  seventh  month  of  fetal  life  and  the  two  halves  are  usually  fused  by  the  seventh 
year. 

Muscles  Attached. — Mm.  corrugator  supercilii,  orbicularis  palpebral  and  tem- 
poralis (three  pairs). 


THE  PARIETAL  BONES  (OSSA  PARLETALES 

The  two  parietal  bones  form  the  lateral  portions  of  the  vault  of  the 
cranium.  Each  has  two  surfaces,  parietal  and  visceral,  and  four 
margins  and  four  angles. 

The  parietal  surface  is  smooth  and  convex  in  both  directions;  its 


44 


OSTEOLOGY 


middle  portion  is  quite  bulged  constituting  the  parietal  tuberosity 
{tuber  parietale).     Between   this  and  the  inferior  margin  are  two 

Sagittal  border 
Parietal  foramen 


Mastoid  angle 


Sphenoidal  angle 

Sulci  arteriosi    Squamosal  border 

Fig.  23.  Sigmoid  groove 

Fig.  22. — The  right  parietal  bone,  outer  surface.     (Sobotta  and  McMurrich.) 
Fig.  23. — Right  parietal  bone,  inner  (cerebral)  surface.     {Sobotta  and  McMurrich. 


nearly  parallel  curved  lines,  the  superior  and  inferior  temporal  lines 
{linea  temporalis  superior  et  inferior).     The  upper  one  serves  for  the 


THE    OCCIPITAL   BONE  45 

attachment  of  the  temporal  fascia  and  the  lower  limits  the  attach- 
ment of  the  m.  temporalis.  The  bone  below  the  inferior  line  (planum 
temporale)  forms  a  part  of  the  floor  of  the  temporal  fossa  and  may 
show  arterial  grooves.  Near  the  occipital  part  of  the  superior  mar- 
gin is  the  parietal  foramen,  for  the  transmission  of  a  small  artery  and 
vein. 

The  cerebral  surface  is  concave  in  both  directions  and  may  show 
impressions  of  the  gyri  of  the  parts  of  the  brain  covered.  The  sur- 
face is  smooth  but  uneven  due  to  the  well-marked  blood-vessel 
grooves  and  arachnoideal  granulations.  Along  the  superior  margin 
is  a  half  groove  (completed  by  the  other  parietal  bone)  constituting, 
when  completed,  the  sagittal  sulcus  [sulcus  sagittal  is)  in  which  is 
lodged  the  superior  sagittal  sinus;  to  the  edges  of  the  groove  the  falx 
cerebri  is  attached.  At  the  mastoid  angle  is  a  portion  of  the  trans- 
verse sulcus. 

The  ventral  (frontal),  superior  (medial)  and  dorsal  (occipital)  mar- 
gins are  deeply  serrated  and  articulate  with  the  bones  indicated. 
The  inferior  margin  (tnargo  squamosus)  is  the  shortest  and  most 
irregular;  it  is  beveled  and  overlapped  by  the  squamous  portion  of 
the  temporal  bone.  The  angles  are  the  frontal,  occipital,  mastoid 
and  sphenoidal  and  indicate  the  bones  with  which  they  articulate. 

Articulations. — Frontally,  with  the  frontal;  medially  with  the  opposite  parietal; 
occipitally,  with  the  occipital;  inferiorly,  with  the  squamous  portion  of  the  tem- 
poral and  the  sphenoid  bone  frontally. 

Ossification. — This  bone  is  purely  of  intramembranous  origin.  Ossification 
starts  at  two  centers  near  the  middle  of  the  bone  at  about  the  eighth  week  of 
fetal  life.  During  the  fourth  month  these  centers  become  confluent  at  the  tuber 
parietale  area.  At  the  angles  ossification  is  not  so  rapid  foreshadowing  the 
fontanelles. 

Muscle  Attached. — Each  affords  attachment  to  the  m.  temporalis. 

OCCIPITAL  BONE  (OS  OCCIPITALE) 

The  occipital  bone  forms  the  dorsoinferior  portion  of  the  cranium 
and  its  four  parts  are  arranged  around  the  foramen  magnum.  The 
four  parts  are  the  tabular,  basilar  and  exoccipiials. 

The  tabular  part  1  squama  occipitalis)  is  convex  in  both  directions. 
It  consists  of  two  parts,  the  occipital  plane  (planum  occipitalc)  which 
is  nearly  vertical  and  the  nuchal  plane  (planum  nuchale)  which  is 
horizontal.  The  dividing  line  between  these  parts  is  represented 
by  the  external  occipital  protuberance  (protnbercntia  occipitalis  ex- 
terna) which  is  near  the  middle  of  the  bone;  the  superior  curved  line 
(liuca  nucha-  superior)  extends  laterally  from  the  protuberance,  on 
each  side.  To  the  protuberance  is  attached  the  ligamentum  nucha?. 
To  the  superior  curved  line  are  attached  the  galea  aponeurotica,  the 
mm.  trapezius,  occipitalis,  sternomastoideus  and  the  splenius  cap- 


46 


OSTEOLOGY 


itis.  The  surface  of  the  planum  occipitale  is  smooth  and  bulging. 
The  planum  nuchale  is  irregular,  rough  and  divided  into  lateral 
halves  by  a  central  crest  {crista  occipitalis  externa)  that  extends  from 
the  protuberance  to  the  foramen  magnum.  Each  area  is  trans- 
versely bisected  by  the  inferior  nuchal  line.  Each  area  gives  attach- 
ment to  the  mm.  semispinalis  capitis,  the  obliquus  capitus  superior 
and  the  rectus  capitis  posterior  major  and  minor. 

The  cerebral  surface  is  concave,  smooth  but  irregular.  A  cross- 
like arrangement  of  ridges  form  the  eminentia  cruciata  at  the  center 
of  which  is  the  internal  occipital  protuberance.  From  the  upper  part 
of  this  extends  the  superior  sagittal  sulcus.  At  right  angles  to  the 
protuberance  extend  the  two  transverse  grooves  {sulci  transversi)  in 

Planum  occipitale 

External  occipital  protuberance 
nuchae  suprcma 
Planum  nuchale 


Condyloid  canal 


Hypoglossal 


Foramen  magnum 
:ipital  bone  seen 


Planum  nuchale 
Lateral  port/o 
Condyloid  fossa 
Jugular  process 

'---  Occipital  condyle? 
External  occipital  crest 
behind.     (Sobotta  and  McMurrich.) 


which  are  lodged  the  transverse  sinuses  and  to  the  edges  of  which  is 
attached  the  tentorium  cerebelli.  Extending  from  the  protuber- 
ance to  the  foramen  magnum  is  seen  the  internal  occipital  crest  to 
which  the  falx  cerebelli  is  attached.  The  area  of  junction  of  the 
sinuses  constitutes  the  confluens  sinuum. 

Of  the  angles  the  superior  is  somewhat  pointed  and  is  inserted  be- 
tween the  parietal  bones  (posterior  fontanelle  region);  the  lateral 
angle  articulates  with  the  petrous  portion  of  the  temporal  bone. 
The  two  serrated  superior  or  parietal  margins  form  with  the  parietal 
bones  the  lamdoidal  suture.  The  lateral  margins  are  irregular  and 
extend  from  the  lateral  angle  on  each  side  to  the  corresponding 
jugular  process  and  they  articulate  with  the  mastoid  portion  of  the 
temporal  bone. 


THE    OCCIPITAL   BOXE 


47 


The  lateral,  or  exoccipital  parts  bound  the  foramen  magnum  later- 
ally. The  inferior  surface  of  each  bears  a  large  condyle  which  serves 
for  articulation  with  the  atlas  of  the  vertebral  column.  Each  con- 
dyle is  oval  or  reniform  and  obliquely  placed;  the  articular  surface 
is  convex-  dorsoventrally  and  flattened  from  side  to  side  and  faces 
downward  and  a  little  laterally.  Each  is  raised  from  the  main  mass 
of  the  exoccipital  and  this  supporting  mass  is  pierced  by  the  hypo- 
glossal canal  (canalis  hypoglossi)  which  transmits  the  hypoglossal 
nerve,  the  meningeal  branch  of  the  ascending  pharyngeal  artery  and 
its  accompanying  vein.  The  canal  terminates  laterally  at  the  ven- 
tral side  of  the  condyle.     Dorsal  to  the  condyle  is  the  condyloid  fossa 

Sagittal  groove 


Lambdoid  border 


Transverse  groovi 


Internal  occipital  crest 


_  Condyloid  canal 
Jugular  tubercle 

Hypoglossal  canal 


Basilar  portion  -r 

jipital  bone  seen  from  in  front  (cerebral  surface).     (Sobotta 
McMurrich.) 


(fossa  condyloidea)  that  may  continue  through  the  bone  as  the  con- 
dyloid canal  [canalis  condyioideus).  Projecting  from  the  bone  at 
the  side  of  each  condyle  is  the  jugular  process  (processus  jugularis) 
which  is  notched  ventrally  to  assist  in  forming  the  jugular  foramen. 
The  cerebral  surface  of  the  exoccipital  is  smooth  but  uneven,  exhibit- 
ing a  projection,  the  jugular  tubercle  (tuberculwn  jugulare)  at  the  side 
of  the  foramen  magnum.  This  is  just  over  the  orifice  of  the  hypo- 
glossal canal  and  it  may  be  grooved  for  the  glossopharyngeal,  vagal 
ami  accessory  nerves. 

The  basilar  portion  forms  the  ventral  boundary  of  the  foramen 
magnum  and  extends  to  the  sphenoid  bone;  to  this  it  is  attached  by  a 
firm  osseous  union.     Its  inferior  surface  is  horizontal,  irregular  and 


46  OSTEOLOGY 

roughened.  In  the  median  line  is  the  pharyngeal  tubercle  for  the 
attachment  of  the  pharyngeal  aponeurosis.  Laterally  the  roughened 
surface  gives  attachment  to  the  mm.  longus  capitis  and  rectus  capitis 
anterior.  The  cerebral  surface  slants  upward  and  forward  and  is 
smooth  and  concave,  contains  the  basilar  groove  and  supports  the 
(medulla)  oblongata. 

The  foramen  magnum  is  oval  and  variable  in  size.  It  is  narrower 
ventrally  than  dorsally  (condylic  encroachment)  and  faces  inferior 
and  somewhat  ventrally.  To  its  margins  are  attached  the  cerebral 
meninges  and  the  ligaments  that  connect  it  to  the  atlas  and  epi- 
stropheus. It  transmits  the  (medulla)  oblongata,  the  cranial  end  of 
the  spinal  cord,  the  accessory  nerves,  the  vertebral  arteries  and  men- 
ingeal vessels. 

Articulations. — With  the  parietals,  temporals,  sphenoid  and  atlas — six  bones. 

Ossification. — It  is  mainly  of  endochondral  origin,  the  squamous  portion, 
above  the  occipital  crest,  developing  intramembranously.  The  basilar  portion 
develops  from  two  renters  (sixth  week;  which  soon  fuse.  Each  exocripital  portion 
ossifies  from  one  renter  (about  the  eighth  week).  The  endochondral  portion  of 
the  squamous  part  ossifies  from  several  centers  (two  to  four  during  the  sixth  or 
seventh  week).  The  superior  part  of  the  bone  arises  in  membrane  from  four 
centers,  two  near  the  midline  (sixth  to  seventh  week)  and  two  more  lateral  to 
these  (third  month).  These  two  lateral  masses  fuse  about  the  fourth  month  of 
fetal  life.  The  exocripital  and  squamous  parts  are  united  by  about  the  third 
year;  the  exoccipitals  and  the  basilar  portion  are  united  by  the  fourth  or  fifth 
year;  the  basilar  part  and  the  sphenoid  bone  fuse  about  the  twenty-fifth  year. 

Muscle  Attached. — To  the  superior  nuchal  line  the  mm.  occipitalis,  the 
trapezius  and  sternomastoideus;  to  the  space  below  this  line  the  mm.  semispinalis 
capitis,  the  splenius  capitis  and  the  obliquus  capitis  superior;  to  the  inferior 
curved  line  and  the  space  below,  mm.  the  rectus  capitis  posterior  major  and  minor; 
to  the  jugular  process  the  mm.  rectus  capitis  anterior  and  the  superior  constrictor 
of  the  pharynx. 

THE  SPHENOID  BONE  (OS  SPHENOIDALE) 

The  sphenoid  bone  is  in  the  base  of  the  skull  and  assists  in  forming  a 
number  of  fossa?.  It  consists  of  a  body,  two  greater,  two  lesser  wings  and 
two  pterygoid  processes.  The  body  (corpus)  is  a  hollow,  cuboidal  mass 
of  bone  placed  in  the  median  line.  It  contains  two  air  sinuses  sepa- 
rated by  a  nearly  vertical  median  septum;  these  are  extensive  and 
communicate  with  the  nasal  fosss.  The  cerebral  surface  is  saddle- 
shaped  and  contains  a  deep  depression,  the  sella  turcica  (fossa  iiy- 
pophyseos)  that  serves  for  the  lodgment  of  the  hypophysis.  The 
dorsal  limit  of  the  fossa  is  a  ridge  of  bone,  the  dorsum  sella:,  which  is 
continuous  with  the  basilar  part  of  the  occipital  bone.  This  is 
smooth  and  supports  the  pons  and  the  basilar  artery.  The  lateral 
portions  of  the  dorsum  sella  project  laterally  as  the  posterior  cli- 
noidal  processes  (processi  clinoidci  posteriores)  and  to  these  the  tento- 
rium cerebelli  is  attached.     The  ventral  boundary  ridge  is  the  tuber- 


THE    SPHENOID    BONE 


49 


culum  sella  in  front  of  which  is  the  sulcus  chiasmatis  that  continues  on 
each  side  into  the  optic  foramen.  In  front  of  the  sulcus  the  bone  is 
smooth  and  continues  for  a  short  distance  and  then  articulates  with 
the  ethmoid.  On  the  irregular  articular  area  there  is  often  a  pro- 
jection in  the  midline  called  the  spine  of  the  sphenoid.  Most  of  each 
lateral  surface  is  fused  with  the  greater  wing  and  pterygoid  process, 
but  curving  above  the  root  of  the  greater  wing  there  is  an  S-shaped 
groove  for  the  internal  carotid  artery  (sulcus  caroticus).  This 
groove  is  bounded  dorsally  by  the  petrous  process  (for  articulation 
with  that  portion  of  the  temporal  bone) ;  above  this  there  may  be 
a  groove  for  the  abducens  nerve.  The  nonarticular  portion  of  the 
anterior  part  is  smooth  and  somewhat  concave  on  each  side  of  the 
midline  due  to  the  presence  of  the  median  sphenoidal  crest  [crista 


Infratemporal  surf  ace 

Sphenomaxillary  surf 

Interna!  pterygoid  phl> 
Fig.   26. — The  sphenoid  bone 


Pterygoid  fist 

ft  niiutar  process 


from  in  front.      (Sobotta  and  McMurrtch.) 


sphenoidalis);  this  articulates  with  the  perpendicular  plate  of  the 
ethmoid.  The  crest  ends  in  the  sphenoidal  rostrum.  At  the  lateral 
limit  of  each  depression  is  seen  an  opening  that  leads  into  the  air 
sinus  of  each  side.  The  remainder  of  this  surface  articulates  with 
the  ethmoid  and  palatal  bones.  The  inferior  surface  presents  a  ridge- 
like continuation  of  the  sphenoidal  rostrum  and  this  ridge  fits  between 
the  alas  of  the  vomer.  The  dorsal  end  of  this  surface  is  rougher  and 
serves  for  the  attachment  of  the  mucosa  of  the  roof  of  the  pharynx. 
The  posterior  surface  of  the  body  is  fused  with  the  basilar  portion  of 
the  occipital  bone. 

The  greater,  or  temporal  wing  (ala  magna)  is  nearly  horizontal  and 
the  cerebral  surface  forms  a  considerable  portion  of  each  middle  fossa 
of  the  skull.  The  lateral,  or  squamosal  margin,  starts  at  the  parietal 
angle  and  downward  and  then  backward  and  medially  to  end  at  the 


5° 


OSTEOLOGY 


spina  angularis  where  the  bone  is  grooved  for  the  cartilaginous  por- 
tion of  the  auditory  tube  (sulcus  tuba).  The  more  extensive  margin 
starts  at  the  parietal  angle,  passes  downward  and  medially  to  the 
body;  the  first  half  (frontal)  articulates  with  the  frontal  bone  while 
the  medial  half  is  free  and  forms  the  inferior  margin  of  the  superior 
orbital  fissure,  which  transmits  the  oculomotor,  trochlear,  ophthal- 
mic division  of  the  trigeminal  and  the  abducens  nerves  and  the 
ophthalmic  veins.  The  margin  then  continues  backward  along  the 
body  of  the  bone  forming,  posteriorly,  the  lingula  that  constitutes 
the  lateral  boundary  of  the  carotid  groove;  this  is  fused  underneath 
with  the  root  of  the  pterygoid  process.  The  remaining  portion  of 
this  margin  is  directed  laterally;  its  first  part  is  free,  forming  the 
anterior  boundary  of  the  foramen  lacerum;  the  rest  (petrosal)  is 


-The  sphenoid  bone  < 


External  /itnygoid  plate 
Htuiititur  process 
l  from  behind.      (Sobotta  and  McMurrich 


rough  for  articulation  with  the  petrous  part  of  the  temporal  bone  and 
ends  as  the  spina  angularis.  In  the  broad  root  of  origin  of  the  greater 
wing  are  seen  three  foramina,  the  foramen  rotundum  (for  the  trans- 
mission of  the  maxillary  division  of  the  trigeminal  nerve);  the  large 
foramen  ovale  (for  the  transmission  of  the  mandibular  division  of  the 
trigeminal  nerve  and  a  branch  of  the  middle  meningeal  artery) ;  the 
foramen  spinosum  (for  the  transmission  of  the  middle  meningeal  artery 
and  vein  and  the  nervus  spinosum,  from  the  mandibular  division  of 
the  trigeminal  nerve).  The  cerebral  surface  of  this  wing  is  concave 
and  exhibits  the  foregoing  foramina  and  may  also  show  impressions 
of  the  gyri  of  the  temporal  lobe  of  the  brain  and  a  sulcus  arteriosus. 
Its  orbital  surface  {fades  orbitalis)  is  smooth  and  forms  a  part  of  the 
orbital  fossa  and  lies  below  and  lateral  to  the  superior  orbital  fissure; 
near  this  there  may  be  the  spina  recti  lateralis  to  which  is  attached 


THE    SPHENOID    BONE  5 1 

the  common  ligament  of  the  ocular  muscles.  Its  inferior  margin 
or  orbital  crest,  is  free  and  assists  in  bounding  the  inferior  orbital 
fissure  (fissura  orbital  is  inferior).  Below  this  is  seen  the  opening  of 
the  foramen  rotundum. 

The  concavo-convex  temporal  surface  (fades  temporalis)  is  the 
largest  and  is  separated  from  the  preceding  by  the  zygomatic  margin. 
The  nearly  horizontal  infratemporal  crest  (crista  infratemporalis)  sepa- 
rates the  planum  temporale  (above)  from  the  infratemporal  surface 
(below).  The  infratemporal  surface  is  divided  by  the  low  spheno- 
maxillary ridge  into  a  lateral,  infratemporal  surface  proper  (showing 
the  openings  of  the  foramina  ovale  and  spinosum)  and  an  anterior, 
medial  spenomaxillary  surface.  The  entire  temporal  surface  enters 
into  the  formation  of  the  infratemporal,  and  pterygopalatine  (spheno- 
maxillary) fossae. 

The  lesser,  or  orbital  wings  (alas  parvae)  are  narrow,  triangular  and 
nearly  horizontally  placed.  Each  arises  by  two  roots  that  embrace 
the  optic  foramen.  The  posterior  root  forms  the  anterior  clinoidal 
process  on  each  side  (processus  clinoideus  anterior).  The  cerebral 
surface  forms  a  part  of  the  anterior  cranial  fossa;  the  inferior  surface 
forms  a  part  of  the  orbit  and  the  upper  boundary  of  the  superior 
orbital  fissure.  Its  anterior  margin  articulates  with  the  frontal  bone 
and  its  posterior,  sickle-shaped  margin  is  sharp  and  separates  the 
anterior  and  middle  cranial  fossae. 

The  pterygoid  processes  (processus  pterygoidei)  are  two  vertical 
processes  that  project  downward  from  the  under  surface  of  the  bone 
at  the  junction  of  the  greater  wings  and  body.  Each  consists  of  two 
lamina,  (lamina:  processus  pterygoidei  lateralis  et  medialis)  between 
the  roots  of  which  extends  the  pterygoid  canal  for  the  pterygoid  nerve 
and  artery.  The  two  plates  are  almost  at  right  angles  to  each  other, 
fused  behind  (except  below  at  the  pterygoid  notch)  and  separated  in 
front  where  they  form  the  pterygoid  fossa.  Thd  medial  pterygoid 
plate  is  narrow  and  stout;  its  posterior  free  margin  forms,  below,  the 
pterygoid  hook  (hamulus  pterygoideus)  and,  above,  it  divides  to  en- 
close the  scaphoid  fossa.  This  fossa  gives  origin  to  the  m.  tensor  veli 
palati.  This  margin  affords  attachment  to  the  pharyngobasilar 
fascia,  pharyngeal  aponeurosis,  superior  constrictor  of  the  pharynx 
and  the  m.  pharyngopalatinus.  At  the  root  of  this  plate  are  the 
vaginal  processes  (processus  vaginalis)  and  the  pterygopalatine  groove. 
The  lateral  pterygoid  plate  is  thin  and  broad  and  is  directed  laterally. 
It  affords  attachment  to  the  inferior  head  of  the  m.  pterygoideus 
lateral  and  to  the  m.  pterygoideus  medialis.  The  anterior  surface  of 
the  root  of  the  pterygoid  process  forms  a  part  of  the  pterygopala- 
tine fossa. 

The  sphenoidal  concha  (concha'  s  phenoidales)  are  hollow  and  each 
is  shaped  like  a  three-sided  pyramid.     The  apex  is  in  contact  with  the 


52  OSTEOLOGY 

vaginal  process  of  the  medial  plate  while  the  base  is  attached  to  the 
lateral  mass  of  the  ethmoid  bone.  The  superior  surface  is  in  contact 
with  the  inferior  surface  of  the  front  part  of  the  body  of  the  sphenoid 
and  the  apposed  walls  have  been  absorbed  to  form  the  sphenoidal 
sinus  of  each  side.  The  inferior  surfaces  assist  in  forming  the  roof  of 
each  nasal  fossa  and  a  part  of  the  pterygopalatine  fossa.  They  are 
separate  bones  up  to  the  fifth  year  at  which  time  fusion,  as  above 
given,  takes  place. 

Articulations. — With  the  frontal,  parietals,  temporals,  occipital,  ethmoid, 
vomer,  palatals  and  zygomatic  bones  (twelve). 

Ossification. — This  bone  is  mainly  of  endochondral  origin,  the  medial  pterygoid 
plate  developing  in  membrane.  There  are  fourteen  centers  of  which  six  form  the 
presphenoid  (the  lesser  wings  and  the  front  part  of  the  body);  the  other  eight 
centers  form  the  postsphenoid,  or  remainder  of  the  bone,  except  the  medial 
pterygoid  plates.  The  first  center  on  each  side  are  for  the  greater  wing  and  it 
appears  about  the  eighth  week  of  fetal  life  and  the  last  ones  are  for  the  hamular 
processes  and  appear  during  the  fourth  fetal  month.  The  centers  are  great 
wings  two,  pot  sphenoid  body  two.  lingular  two,  lesser  wings  two,  presphenoid 
body  two,  medial  pterygoid  plates  two,  hamular  processes  two.  The  presphe- 
noid and  main  part  of  the  body  unite  about  the  eighth  month  of  fetal  life  so  that 
at  birth  the  greater  wings  with  the  pterygoid  processes  are  still  separate  from 
the  body;  they  are  all  united  usually  by  the  end  of  the  first  year. 

Muscle  Attached. — Mm.  temporalis,  pterygoideus  lateralis,  pterygoideus 
medialis,  constrictor  pharyngeus  superior,  tensor  veli  palati,  levator  palpebrae, 
obliquus  superior  and  the  four  recti  of  the  eyeball  (eleven  pairs). 

THE  TEMPORAL  BONES  (OSSA  TEMPORALLY) 

The  temporal  bones  form  the  middle  portion  of  the  base  of  the 
cranium.  Each  consists  of  three  parts — the  squamous,  tympanic 
and  petromastoid  portions. 

The  squamous  part  (squama  temporalis)  is  the  vertical  portion 
that  forms  part  of  the  lateral  boundary  of  the  cranium.  The  cere- 
bral surface  is  smooth  but  bears  the  impressions  of  the  gyri  of  the 
temporal  lobe  of  the  brain  and  the  middle  meningeal  artery.  The 
temporal  surface  is  smooth  and  assists  in  forming  a  part  of  the  tem- 
poral fossa;  here  it  gives  attachment  to  the  m.  temporalis.  At  the 
anteroinferior  part  of  this  surface  is  the  zygomatic  process  (processus 
zygomaticus).  This  is  a  twisted  bar  of  bone  that  at  its  anterior  ex- 
tremity articulates  with  the  zygomatic  bone;  its  inferior  and  medial 
aspects  give  attachment  to  the  m.  masseter.  Its  superior  margin 
continues  backward  over  the  external  acoustic  meatus  as  the  superior 
root  of  the  zygomatic  process  and  becomes  continuous  with  the  supra- 
mastoid  crest.  The  inferior  margin  turns  medially  and  constitutes 
the  anterior  root.  About  half  way  along  this  margin  is  the  lubcrcu- 
lum  articulate  that  bounds  the  mandibular  fossa  (fossa  mandibularis) 
in  front.  Just  in  front  of  the  external  auditory  meatus  the  anterior 
root  has  another  projection,  the  postglenokl  tubercle.     In  the  depths 


THE    TEMPORAL   BONES 


53 


of  this  fossa  is  the  partly  closed  petrotympanic  fissure,  the  middle 
portion  of  which  transmits  the  tympanic  branch  of  the  internal  max- 
illary artery  and  also  lodges  the  anterior  process  of  malleus.  Near% 
this  is  a  canaliculus  that  transmits  the  chorda  tympani  nerve.  That 
portion  of  the  mandibular  fossa  behind  the  fissure  is  nonarticular 
and  lodges  a  portion  of  the  parotid  gland  (which  becomes  enlarged 
in  mumps  and  causes  the  pain  when  the  mandible  is  lowered).  The 
anterior  part  is  articular  and  with  the  articular  tubercle  and  the 
condyle  of  the  mandible  forms  the  temperomandibular  articulation; 
this  contains  an  interarticular  fibrocartilage.  The  posteroinjerior 
surface  of  the  squamosa  forms  a  part  of  the  posterior  wall  of  the  ex- 
ternal auditory  canal.  The  superior  margin  is  convex  and  beveled 
at  expense  of  the  cerebral  surface.     The  posterior,  inferior  and  medial 

Parietal  border 
%  Squamous  portion 

Groove  for  middle  temporal  artery 


Parietal 
Supramental 


Sphenoidal  border 


from  the  outer  (lateral) 
ilc.Murricli.) 

margins  of  the  squama  are  fused  with  the  petrous  part.  Inferiorly 
and  in  front  is  the  petrotympanic  fissure  separating  it  from  the  cor- 
responding part  of  the  bone. 

The  tympanic  portion  (pars  tympanica)  forms  the  posterior  part 
of  the  mandibular  fossa,  the  anterior  and  inferior  walls  and  a  part 
of  the  posterior  wall  of  the  external  auditory  canal.  Its  lower  edge 
embraces  the  styloid  process  as  the  vagina!  process.  Although  fused 
with  the  other  parts  of  the  bone  it  is  separated,  laterally,  from  the 
mastoid  and  squamous  divisions  by  the  tympanomastoid  fissure.  To 
that  part  bounding  the  canal  the  cartilaginous  portion  of  the  external 
ear  is  attached. 

The  external  auditory  canal  {meatus  audilorius  externus)  is  slightly 
curved,  oval  on  section  and  twisted  upon  its  long  axis.  For  details 
see  page  350. 


54  OSTEOLOGY 

The  petromastoid  portion  (pars  petrosa  et  pars  mastoidia)  is  the 
most  massive  division  and  is  pyramidal  in  form.  The  petrous  part 
(pyramis)  is  a  long,  three.-sided  pyramid  with  an  apex,  a  base,  three 
surfaces  and  three  margins.  The  apex  is  near  the  middle  line  of  the 
base  of  the  cranium  at  the  body  of  the  sphenoid.  The  base  is  fused 
with  the  squamous  and  tympanic  portions.  The  anterior  surface 
forms  a  part  of  the  floor  of  the  middle  cranial  fossa  and  is  smooth  but 
irregular;  it  may  show  impressions  of  the  gyri  of  the  temporal  lobe  of 
the  cerebrum.  Near  the  apex  is  the  impressio  trigemina  which 
lodges  the  semilunar  ganglion  of  the  trigeminal  nerve.  On  this 
surface  are  seen  the  eminentia  arcuata,  made  by  the  superior  semi- 
circular canal;  near  this  is  the  slit-like  hiatus  canalis  facialis,  for  the 
facial  nerve;  a  little  lateral  to  the  hiatus  may  be  a  small  opening,  the 


Sulcus  arteriosus     4 
Sphenoidal  border 


,.  Parietal  border 

Cerebral  sar/at 


Subarcuate  Jossa 
Internal   auditory  meatus 

Inferior  petrosal  groove 

Styloid  proa 


Fig.  20. — The  right  temporal  bone 


seen  from  the  cerebral  surface.      (Sobotta  and 
\L  Murrich.) 


apcrtura  superior  canalis  tympani.  The  posterior  surface  forms  part 
of  the  posterior  cranial  fossa  and  is  concave,  smooth  but  uneven. 
Here  the  following  are  seen:  (i)  Internal  auditory  meatus  (meatus 
auditorius  internus)  a  long,  oval  opening  in  the  depths  of  which  the 
opening  of  the  canalis  facialis  may  often  be  noted.  The  meatus 
transmits  the  acoustic  nerve  and  vessels.  (2)  The  aqueduct  of  the 
vestibule  (apertura  externa  aqueduclus  vestibuli)  is  in  front  of  the  pre- 
ceding; this  lodges  the  saccus  endolymphaticus.  (3)  The  ridge  of 
the  posterior  semicircular  canal  is  above  this.  The  inferior  surface 
is  very  irregular  and  mostly  rough.  The  most  prominent  structure 
is  the  styloid  process  (processus  styloideus)  that  gives  attachment  to 
the  mm.  styloglossus,  stylohyoideus  and  stylopharyngeus  and  the 


THE    TEMPORAL    BOXES 


55 


stylohyoid  and  stylomaxillary  ligaments.  Behind  the  process  is  the 
foramen  styloideum,  for  the  facial  nerve  and  the  mastoid  artery.  The 
jugular  fossa  (fossa  jugularis)  is  medial  to  the  process  and  assists  in 
forming  the  jugular  foramen.  In  the  jugular  fossa  is  the  canalis 
mastoideus  for  the  auricular  branch  of  the  vagus.  In  front  of  and 
lateral  to  the  fossa  is  the  carotid  canal  (canalis  caroticus)  for  the  trans- 
mission of  the  internal  carotid  artery  and  the  sympathetic  plexus. 
Upon  the  ridge  separating  the  fossa  and  canal  is  the  canaliculus 
tympanicus  for  the  transmission  of  the  tympanic  branch  of  the  glosso- 
pharyngeal nerve.  The  fossula  fenestra  cochlea,  with  the  opening  of 
the  aqueduct  of  the  cochlea  (apertura  externa  aqueductus  cochlea), 
are  seen  anteromedial  to  the  jugular  fossa.     In  the  fossula  is  lodged 


•--.^Sphenoidal  border 


Fig.  30. — Right  temporal  bone  seen  from  below.     {Sobolta  and  McMurrich.) 


the  petrous  ganglion  of  the  glossopharyngeal   nerve.     From  the 
roughened  bone  near  the  apex  the  m.  tensor  veli  palatini  arises. 

The  superior  angle,  or  margin,  separates  the  anterior -and  posterior 
surfaces  and  also  separates  the  middle  and  posterior  cranial  fossae 
from  each  other.  It  is  grooved  for  the  superior  petrosal  si?ius  and  to 
it  is  attached  the  tentorium  cerebelli.  The  posterior  angle,  or  mar- 
gin, is  in  part  free  or  nonarticular  where  it  forms  a  part  of  the  jugular 
foramen;  the  remainder  is  articular  and  usually  presents  a  groove 
for  the  inferior  petrosal  sinus.  The  anterior  angle,  or  margin,  is  the 
shortest  and  extends  from  the  apex  to  the  squamous  part.  Near 
the  squama  is  seen  the  osseous  portion  of  the  auditory  tube  (canalis 
musculotubarius).  This  is  divided  by  a  bony  septum  into  a  smaller 
division  (semicanalism.  tensor  tympani)  for  the  tensor  tympani  muscle; 


56  OSTEOLOGY 

the  larger  portion  {semicanalis  tubes  auditiva)  is  the  osseous  portion 
of  the  pharyngotympanic,  or  auditory  tube. 

The  mastoid  portion  of  the  temporal  bone  lies  posterior  to  the  ex- 
ternal auditory  meatus  and  forms  a  nipple-like  process  that  is  vari- 
able in  size.  Its  lateral  surface  is  rough  and  with  the  inferior  margin 
affords  insertion  to  the  mm.  sternomastoideus,  splenius  capitis  and 
longissimus  capitis.  Its  inferior  surface  shows  a  groove  (incisura 
mastoidea)  along  the  root  of  the  apex  which  gives  origin  to  the  pos- 
terior belly  of  the  m.  digastricus.  Medial  to  this  groove  is  another 
for  the  occipital  artery.  The  cerebral  surface  of  the  mastoid  division 
forms  a  part  of  the  floor  of  the  posterior  cranial  fossa;  on  it  are  seen 
a  deep  wide  groove  for  the  transverse,  or  sigmoid  sinus  which  leads 
to  the  jugular  fossa;  the  mastoid  foramen  for  a  small  artery  and  vein. 

Articulations. — Each  articulates  with  the  occipital,  parietal,  sphenoid,  man- 
dible and  zygomatic  bones  (5). 

Ossifications. — It  is  mainly  of  endochondral  origin  and  develops  from  ten 
centers,  as  follows:  (a)  the  center  for  the  squamozygomatic  part  appears  at  about 
the  end  of  the  second  month  of  fetal  life;  (b)  one  for  the  tympanic  plate  during  the 
third  month;  (f)  six  for  the  petromastoid  portion  during  the  fifth  to  the  sixth 
months;  (d)  two  for  the  styloid  process,  one  just  before  and  the  other  just  after 
birth.  The  squamozygomatic  portion  develops  in  membrane.  The  mastoid 
process  develops  during  the  second  year  and  toward  the  age  of  puberty  it  be- 
comes cellular.  The  squamous  and  tympanic  parts  fuse  just  before  birth  and 
the  petromastoid  and  the  squama  during  the  first  year.  The  base  of  the  mastoid 
process  fuses  with  the  rest  about  the  same  time  and  the  lower  end  of  the  styloid 
process  and  the  basal  end  unite  about  the  age  of  puberty. 

Muscles  Attached. — To  the  squama,  the  m.  temporalis;  to  the  zygomatic 
process,  the  m.  masseter;  to  the  mastoid  portion,  mm.  sternomastoideus,  splenius 
capitis,  longissimus  capitis,  digastricus  and  auricularis  posterior;  to  the  styloid 
process;  the  mm.  styloglossus,  stylohyoideus  and  stylopharyngeus;  to  the 
petrous  portion  the  mm.  tensor  veli  palatini,  stapedius,  the  tensor  tympani  and 
levator  veli  palatini  (fifteen). 

THE  ETHMOID  BONE  (OS  ETHMOIDALE) 

The  ethmoid  bone  is  alight,  thin-walled,  honeycombed  bone  that 
forms  a  part  of  the  floor  of  the  anterior  cranial  fossa  and  fits  in  be- 
tween the  orbital  parts  of  the  frontal  bone.  The  bone  is  T-like  and 
consists  of  a  median  vertical  plate  that  is  topped  by  the  cribriform 
plate.     From  this  the  ethmoidal  labyrinth  of  each  side  is  suspended. 

The  perpendicular  plate  {lamina  perpendicularis)  is  irregular  and 
pentagonal  in  form  and  projects  into  the  cranial  cavity  as  a  sharp, 
median  crest  (crista  galli);  to  this  is  attached  the  falx  cerebri,  at  its 
frontal  extremity  is  a  notch  forming  the  foramen  cecum  with  the 
frontal  bone.  This  plate  is  usually  deflected  to  one  or  the  other  side 
and  has  smooth  surfaces.  Its  posteroinferior  surface  is  fused  with  the 
vomer  while  its  anterior  margin  articulates  with  the  cartilaginous 
nasal  septum. 


THE    ETHMOID    BONE 


57 


The  cribriform  plate  (lamina  cribrosa)  bridges  the  space  between 
the  two  orbital  plates  of  the  frontal  bone  and  is  pierced  by  numer- 
ous foramina  for  the  passage  of  the  olfactory  nerves.  On  each  side  of 
the  midline  the  cerebral  surface  shows  a  groove  for  the  olfactory  lobe. 
Along  each  lateral  edge  are  notches  that  become  the  ethmoidal  for- 
amina upon  articulation.  Anteriorly,  there  is  a  slit  that  transmits 
the  nasociliary  nerve  into  the  nose.  The  inferior  surface  forms  the 
roof  of  the  nasal  fossa?. 

The  ethmoidal  labyrinths  (labyrinthi  cthmoidaJes)  are  two  thin- 
walled  masses  enclosing  numerous  air  cells,  anterior,  middle  and  pos- 
terior.    The  lateral,  or  orbital  wall  (lamina  papyracea)  forms  a  part 


Lamina  papyracea 


dtcular 

Middle 

'""   }    *             turbinated 

Ethmoidal 

cell 

Perpen- 

Uncinate 

dicular 

process 

plate 

Fig.  31. — The  ethmoid  bone  seen  from 
above.     (Sobolta  and  McMurrich.) 


12. — The  ethmoid  bone  seen  from  the 
;ide.     (Sobolta  and  McMurrich.) 


of  the  medial  wall  of  the  orbit.  The  anterior  and  posterior  ethmoidal 
foramina  are  seen  here;  these  transmit  small  ethmoidal  vessels 
and  the  anterior  nasociliary  nerves.  Upon  the  medial  surface,  that 
forms  a  part  of  the  lateral  wall  of  each  nasal  fossa,  are  seen  the  two 
ethmoidal  turbinals  [concha  ethmoidales).  These  are  two  thin,  con- 
voluted plates  of  bone  of  which  the  middles  is  much  the  larger. 
Between  the  middle  and  superior  concha?  is  the  superior  meatus  of 
the  nasal  fossa  and  into  this  the  posterior  ethmoidal  cells  open.  The 
middle  meatus  lies  between  the  middle  and  inferior  conchas  and 
into  it  open  the  middle  and  anterior  ethmoidal  cells  and  the  frontal 
sinus  (see  "Nasal  Fossaa,  page  272). 

Articulations. — With  the  sphenoid  frontal,  two  nasal,  two  palatal,  two  lacrimal, 
two  maxilkc,  two  inferior  concha?  and  vomer  bones  (thirteen). 

Ossification. — It  is  of  endochondral  origin  and  is  developed  for  jour  centers, 
one  for  each  labyrinth  and  two  for  the  perpendicular  plate.  The  centers  for  the 
labyrinths  appear  at  about  the  fifth  month  of  fetal  life  and  also  form  the  lateral 
part  of  the  perpendicular  plate.  The  centers  for  the  perpendicular  plate  appear 
at  the  end  of  the  first  year;  they  form  this  plate  and  the  medial  portion  of  the 


58  OSTEOLOGY 

cribriform  plate.     Fusion  of  all  parts  is  complete  by  the  sixth  year.     The  sphe- 
noidal fusion  is  complete  by  about  the  twenty-fifth  year  but  vomerine  fusion  is 
not  completed  until  the  fortieth  or  fiftieth  year.     The  ethmoidal  cells  are  usually 
completed  at  birth. 
Muscles  Attached. — Xone. 

THE  INFERIOR  CONCHiE  (CONCHA  NASALES  INFERIOR) 

Each  inferior  concha  is  a  scroll-shaped  bone  located  on  the  lateral 
wall  of  the  inferior  part  of  the  nasal  fossa.  The  superior  margin  is 
thin  and  articulates  with  the  maxilla  and  the  palatal  bone  and  by  a 
process  {processus  lacrimalis)  with  the  lacrimal  bone.  Here  it  assists 
in  forming  the  nasolacrimal  canal.  Its  posterior  edge  unites  with  the 
ethmoid  bone  by  means  of  the  ethmoidal  process  (processus  ethmoid- 
alis).     From  this  margin  the  maxillary  process  extends  forming  a  part 

Ethmoidal  process 

Lachrymal  process 


Maxillary  process 

Fig.  33. — The  inferior  turbinated  (conchal)  bone  seen  from  its  lateral  surface.     (Sobotta  and 
M<  Murrich.) 

of  the  medial  wall  of  the  maxillary  sinus.  The  medial  margin  is  free 
and  slightly  curved.  The  medial  surface  is  convex  from  above  down- 
ward, projects  into  the  nasal  fossa  and  forms  the  floor  of  the  middle 
meatus.  The  lateral  surface  is  concave  and  overhangs  the  inferior 
meatus. 

Articulations. — With  the  maxilla,  lacrimal,  ethmoidal  and  palatal  bones  (four). 
Ossification. — It  is  developed  in  cartilage  and  from  a  single  center.     This 
appears  at  about  the  fifth  montli  of  fetal  life. 
Muscles  Attached. — None. 

LACRIMAL  BONES  (OSSA  LACRLMALIA) 

The  lacrimal  bones  are  thin  bones  that  form  a  part  of  the  orbital 
fossas.  Each  has  two  surfaces  and  four  margins  and  is  quadrilateral 
in  shape. 

The  lateral,  or  orbital  surface,  is  smooth  and  is  divided  by  a  vertical 
ridge  (crista,  lacrimalis  posterior)  into  two  areas;  the  anterior  is  the 
lacrimal  groove  (sulcus  lacrimalis)  for  the  lacrimal  sac;  the  posterior 
area  is  the  orbital  surface  proper.  The  ridge  ends  below  in  a  hooklet 
(hamulus  lacrimalis)  that  forms  part  of  the  upper  boundary  of  the 
nasolacrimal  duct.  The  medial  wall  of  the  lacrimal  groove  ends  as 
the  descending  process.     Part  of  the  crest  gives  attachment  to  the 


THE   VOMER  59 

tendo  oculi  and  lacrimal  part  of  the  m.  orbicularis  oculi.  The 
medial  surface  is  uneven  and  closes  in  the  anterior  ethmoidal  cells  and 
forms  a  part  of  the  lateral  boundary  of  the  middle  meatus  of  the  nose. 
The  margins  are  uneven  and  articulate  with  various  bones. 

Articulations. — With  the  frontal,  ethmoidal,  maxilla  and  inferior  concha  (four). 
Ossification. — Of  intramembranous  origin  and  from  one  center  that  appears 
during  the  eighth  or  ninth  week  of  fetal  life. 

Muscles  Attached. — M.  orbicularis  oculi  (lacrimal  part). 


'X. 


Posterior 

lachrymal 

crest 


Alae  vomeris 


Depression  for 
lachrymal  sac 


Hamulus  lacrimalis 


Fig.   34. — Left   lacrimal    bone    seen  PlG.    !5. — The  vomer  seen  from  the  side, 

from    its     median     surface.     (Sobotta  fScbotta  and  McMurrich.) 

and  McMurrich.) 


THE  VOMER 

The  vomer  is  an  irregular,  quadrilateral  bone  that  forms  the  pos- 
terior portion  of  the  nasal  septum.  It  is  usually  deflected  to  one  or 
the  other  side.  The  right  and  left  surfaces  are  smooth.  The  superior 
margin  possesses  two  lips,  or  alee  by  means  of  which  it  is  held  fixedly 
in  position.  The  posterior,  or  free  margin  is  the  posterior  margin  of 
the  nasal  septum  and  separates  the  two  choanae.  The  inferior 
margin  is  irregular  for  articulation  with  the  palatal  bones  and  the 
maxillae.  The  anterior  (longest)  margin  is  sloping  and  articulates 
with  the  ethmoidal  bone  and  the  cartilaginous  nasal  septum.  Its 
anterior  extremity  is  irregular  and  articulates  with  the  maxillae. 

Articulations. — With  the  maxilla?,  palatals,  sphenoid  and  ethmoid  bones  (six.) 

Ossification. — It  is  of  intramembranous  origin  and  developes  from  two  centers 

(one  on  each  side  of  the  midline).     These  appear  during  the  end  of  the  second 

month.     These  centers  begin  to  fuse  during  the  third  fetal  month  and  fusion  is 

usually  completed  at  the  age  of  puberty. 

Muscles  Attached. — None. 

NASAL  BONES  (OSSA  NASALES) 

The  two  nasal  bones  form  the  bridge  of  the  nose.  Each  has  two 
surfaces  a.nd  four  fnargins.  The  lateral  surface  is  convex  from  side  to 
side,  concave  from  above  downward  and  constricted  near  the  middle. 
Upon  this  surface  is  seen  a  small  opening  for  the  nutrient  vessel. 


6o 


OSTEOLOGY 


The  medial  surface  is  small,  concave  from  side  to  side  and  forms  a 
part  of  the  lateral  boundary  of  the  nasal  fossa.  It  is  traversed  bv  a 
narrow  groove  (sulcus  ethmoidalis)  in  which  is  lodged  a  branch  of  the 
nasociliary  nerve.  The  margins  are  roughened  and  irregular  for 
articulation  with  the  neighboring  bones. 

Articulations. — With  the  opposite  nasal,  the  frontal,  ethmoidal  and  maxilla 
(four). 

Ossification. — It  is  of  intramembranous  origin  and  is  developed  from  one 
center  that  appears  about  the  eighth  week  of  fetal  life. 

Muscles  Attached. — Xone. 


Nasal  foramen  • 


Fig.  36. — The  left  nasal  bone  seen 
:rom  the  lateral  surface.  {Sobolla 
md  McMurrich.) 


■  Ethmoidal  groove 


[Nasal  foramen 

Fig.  37. — The  left  nasal  bone  seen 
rom  its  medial  surface.  (Sobotta 
nd  McMurrich.) 


THE  FACIAL  BONES  (OSSA  FACIEI) 

These  comprise  the  two  maxillae,  two  palatals,  two  zygomatics  and 
the  mandible. 

THE  MAXILLAE 

The  maxilla?  (two)  form  the  front  of  the  face  and  constitute  the 
upper  jaw.  The  main  portion  is  the  body,  and  from  this  extend  four 
processes.  The  body  (corpus)  although  apparently  massive  is  light 
and  hollow  (maxillary  sinus).  It  has  four  surfaces.  The  lateral,  or 
anterior  surface  [fades  anterior)  although  smooth  is  irregular  showing 
ridges  that  correspond  to  the  sockets  of  the  teeth  (processus 
alveolaris).  Of  these  ridges  that  for  the  canine  tooth  is  the  most 
prominent  separating  two  fossae,  incisor  fossa  (medially)  and  canine 
fossa  (laterally).  Its  superior  oblique  margin  (margo  infraorbital  is) 
is  free  and  beneath  it  is  the  infraorbital  foramen.  The  medial  margin 
has  the  nasal  notch  limited  below  by  the  anterior  nasal  spine. 

The  orbital  surface  (planum  orbitale)  is  smooth  and  nearly  horizon- 
tal. Posteriorly  it  forms  part  of  the  posterior  boundary  of  the  in- 
ferior orbital  fissure.  The  first  part  of  the  medial  margin  is  notched 
forming  the  lacrimal  groove  (sulcus  lacrimalis) .  Through  the  planum 
extends  the  infraorbital  canal  which  may  be  open  for  a  variable  dis- 
tance.    The  canal  has  two  openings  (invisible  unless  the  canal  is  laid 


THE    MAXILL.* 


6l 


open)  that  lead  into  the  maxillary  sinus  and  these  transmit  vessels  to 
the  anterior  and  middle  teeth. 

The  infratemporal  surface  is  posteriorly  and  laterally  placed,  convex 
from  side  to  side  and  smooth.  The  upper  margin,  with  the  posterior 
margin  of  the  orbital  surface,  forms  the  anterior  boundary  of  the 
inferior  orbital  fissure.  Near  the  middle  of  the  posterior  portion  it  is 
pierced  by  several  alveolar  canals  (foramina  aheolaria)  that  trans- 
mit vessels  and  nerves  to  the  molar  teeth.     That  part  of  the  bone 


Frontamaxiltary  suture 


Frontal  process 

% 


Fig.  38. — The  right  maxilla  seen  from  the 
medial  surface.     (Sobotla  and  McMurrich.) 


FlG.  39. — The  right  maxilla  seen  from 
the  lateral  surface.  (Sobotta  and  Mc- 
Murrich.) 


that  extends  beyond  the  last  molar  tooth  is  called  the  maxillary 
tuberosity  (tuber  maxillare). 

The  nasal,  or  medial  surface  (fades  nasalis)  forms  a  part  of  the 
lateral  wall  of  the  nasal  fossa.  It  exhibits  the  nasal  notch,  in  front, 
the  lacrimal  groove,  above,  and  along  the  posterior  margin  the  ptery- 
gopalatine groove,  which  becomes  a  canal  upon  articulation  (for  the 
posterior  palatine  nerve  and  the  great  palatine  artery).  Near  the 
upper  and  back  part  of  this  surface  is  the  opening  into  the  maxillary 
sinus  which  is  smaller  in  the  articulated  skull.  The  sinus  is  pyra- 
midal in  shape  (as  is  the  body)  and  communicates  with  the  middle 
meatus  of  the  nasal  fossa.  Its  walls,  the  surfaces  of  the  body,  are 
for  the  most  part  thin,  especially  over  the  sockets  of  the  teeth.     In 


62  OSTEOLOGY 

the  recent  state  it  is  lined  with  a  mucous  membrane  which  is  con- 
tinuous with  that  of  the  nasal  fossa. 

The  palatal  process  is  a  horizontal  shelf  of  bone  at  the  lower  margin 
of  the  nasal  surface  of  the  body  and  extends  as  far  back  as  the  second 
molar  tooth.  Its  superior  surface  forms  most  of  the  floor  of  the  nasal 
fossa.  The  rough  inferior  surface  is  concave  from  side  to  side  and, 
with  its  fellow,  forms  the  anterior  three-fourths  of  the  vault  of  the 
hard  palate  and  about  one-half  of  the  roof  of  the  oral  cavity.  It  is 
grooved  by  the  pterygopalatine  groove.  Its  medial  margin  helps 
form  the  nasal  crest  {crista  nasalis)  for  articulation  with  the  vomer. 
In  front  the  nasal  crest  forms  the  incisor  crest  that  ends  in  the  anterior 
nasal  spine.  Back  of  the  nasal  spine  the  medial  margin  is  grooved 
and  with  its  fellow  forms  the  incisive  foramen  (foramen  incisivum). 
Into  this  open  the  foramina  of  Stenscn  and  Scarpa. 

The  alveolar  process  (processus  alveolaris)  is  that  part  below  the 
level  of  the  palatal  process.  It  represents  half  of  the  superior  dental 
arch  and  bears  the  teeth  of  its  respective  side.  It  is  present  only 
when  the  teeth  are  present,  being  absorbed  when  the  permanent 
teeth  are  lost. 

The  zygomatic  process  (processus  zygomaticus)  is  concave  behind, 
in  keeping  with  the  infratemporal  surface,  and  flattened  anteriorly. 
It  separates  the  facial  and  infratemporal  surfaces  and  is  attached 
to  the  body  above  the  first  molar  tooth.  Its  extremity  is  irregular 
for  articulation  with  the  zygomatic  bone. 

The  frontal  process  (processus  frontalis)  is  a  thin  plate  of  bone  ex- 
tending above  the  level  of  the  orbital  surface.  The  infraorbital 
margin  is  continued  upon  it  as  the  crista  lacrimalis  anterior,  behind 
which  the  grooved  area  forms  a  part  of  the  fossa  for  the  lacrimal  sac. 
The  tendo  oculi  is  attached  in  front  of  the  groove.  The  medial  sur- 
face is  smooth  but  uneven  forming  part  of  the  lateral  boundary  of 
the  nasal  fossa.  Upon  it  is  seen  the  oblique  ethmoidal  crest  (agger 
nasi).  Its  edges  are  roughened  for  articulation  with  the  neighboring 
bones. 

Articulations. — It  articulates,  above,  with  the  nasal,  frontal,  lacrimal  and 
ethmoidal  bones;  posteriorly  and  medially  with  the  palatal  and  opposite  maxilla; 
laterally  with  the  zygomatic  bone;  it  also  articulates  with  the  inferior  concha  and 
the  vomer  (nine). 

Ossification. — It  is  of  intramembranous  origin  and  is  developed  from  six 
centers.  These  are  the  orbitonasal,  zygomatic,  palatal,  nasal,  injrawmerine  and 
prcmaxillary  (probably  two).  These  centers  appear  about  the  eighth  week  and 
by  the  tenth  week  the  first  five  have  fused  into  one  mass.  Later  these  two  fuse 
but  the  suture  between  them  is  noted  on  the  -palate  up  to  middle  life.  The 
maxillary  sinus  begins  to  form  during  the  fourth  month  and  reaches  its  full 
size  after  the  second  dentition. 

Muscles  Attached. — Mm.  orbicularis  oculi,  obliquus  inferior,  caput  angulare, 
caput  infraorbitale,  caninus,  nasalis,  depressor  alae  nasi,  dilatator  naris  posterior, 
masseter,  buccinator,  orbicularis  oris  and  pterygoideus  medialis  (twelve). 


THE    PALATAL    BONES 


63 


PALATAL  BONES   (OSSA  PALATLNA) 

Each  palatal  bone  is  very  delicate  and  of  irregular  shape.  It 
assists  in  forming  the  following  fossae:  nasal,  orbital,  pterygopalatine, 
infratemporal  and  pterygoid.  It  has  two  main  portions,  horizontal 
and  vertical. 

The  horizontal  portion  (pars  horizontalis)  forms  about  one-third 
of  the  hard  palate.  Its  superior  surface,  smooth  and  concave,  con- 
stitutes a  part  of  the  floor  of  the  nasal  cavity.  The  inferior  surface 
is  rougher  and  forms  part  of  the  roof  of  the  mouth.  The  medial 
and  anterior  margins  articulate  with  the  neighboring  bones  while  the 
lateral  margin  fuses  with  the  pars  perpendicularis.  The  posterior 
margin  is  free  and  has  the  aponeurosis  of  the  palate  attached  to  it. 


Orbital  process  — 


Sphenoidal  process 


Orbital 
process 
Horizontal  plate^ 


Pterygopalatine  groove 
Perpendicular  plate 

Orbital  process 


Pterygopalatine  groove  Lesser  palatine 

(greater  palatine  foramen)  foramen 

Fig.  41.  Fig.  42. 

Fig.  40. — The  right  palate  bone  seen  from  behind.     (Sobotla  and  McMurrich.) 
Fig.  41. — The  right  palate  bone  seen  from  lateral  surface.     (Sobotta  and  McMurrich.') 
Fig.  42. — The  right  palate  bone  seen  from  the  medial  surface.    *,  Surface  which  completes 
the  pterygoid  fossa.     (Sobotla  and  McMurrich.) 


The  posterior  part  of  the  medial  margin  constitutes  the  posterior 
nasal  spine. 

The  perpendicular  portion  (pars  perpendicularis)  is  narrow  below. 
Its  medial  surface  forms  the  back  of  the  lateral  wall  of  the  nasal  fossa 
and  is  crossed  by  the  conchal  crest  (crista  conchalis) ;  above  this  crest 
is  the  middle  meatus  and  below  it  is  the  inferior  meatus.  Near  its 
upper  part  is  the  ethmoidal  crest.  The  lateral  wall  is  a  part  of  the 
pterygopalatine  fossa  wall.  It  is  quite  irregular  and  shows  the  ptery- 
gopalatine groove.  Its  front  part  constitutes  the  maxillary  process. 
The  anterior  margin  is  irregular  for  articulation.  The  posterior  mar- 
gin exhibits,  below,  the  pyramidal  process.     The  inferior  margin  joins 


64  OSTEOLOGY 

the  horizontal  part.  The  superior  margin  supports  two  processes, 
the  sphenoidal  and  orbital. 

The  sphenoidal  process  (processus  sphenoidalis)  is  small  and  dor- 
sally  directed.  Its  superior  surface  is  smooth  and  assists  in  forming 
the  pharyngeal  canal  for  the  pharyngeal  artery  and  the  pharyngeal 
branch  of  the  sphenopalatine  ganglion.  Its  medial  surface  forms  a 
part  of  the  nasal  fossa.  Its  lateral  surface  forms  a  part  of  the  wall 
of  the  pterygopalatine  fossa. 

The  hollow  orbital  process  (processus  orbitalis)  is  the  highest  part 
of  the  bone  and  its  medially  directed  opening  communicates  with 
the  sphenoidal  sinus.  The  nonarticular  surfaces  are  as  follows: 
superior,  that  forms  a  part  of  the  floor  of  the  orbit;  medial,  that 
forms  a  part  of  the  lateral  nasal  wall;  lateral,  that  forms  a  part  of 
the  wall  of  the  pterygopalatine  fossa. 

The  pyramidal  process  (processus  pyramidalis)  is  at  the  antero- 
inferior extremity  of  the  bone.  A  smooth,  V-shaped  groove  forms 
a  part  of  the  pterygoid  fossa.  A  small  part  of  the  lateral  surface 
enters  into  the  formation  of  the  infratemporal  fossa.  Through  this 
process  pass,  vertically,  the  lesser  palatine  foramina  for  the  trans- 
mission of  the  lesser  palatine  nerves  and  vessels. 

Articulations. — With  the  ethmoid,  vomer,  sphenoid,  maxilla,  inferior  concha 
and  the  opposite  palatal  bones  (six). 

Ossification. — It  is  of  intramembranous  origin  and  usually  from  one  center, 
which  appears  in  the  second  fetal  month.  The  orbital  process  may  have  a 
separate  center. 

Muscle  Attached. — The  mm.  tensor  veli  palatini,  constrictor  pharyngeus 
superior,  pterygoideus  medialis  and  uvula;  (four). 

THE  ZYGOMATIC  BONES  (OSSA  ZYGOMATIC  A) 

The  zygomatic  bones  are  irregular,  constituting  the  cheek  bones 
and  assisting  in  forming  the  orbital,  infratemporal  and  temporal 
fossa?. 

The  lateral  surface  (fades  malaris)  of  each  is  convex,  smooth  and 
exhibits  the  zygomaticofacial  canal.  The  most  prominent  part  of 
this  surface  is  the  malar  tuberosity.  The  surface  is  roughly  quad- 
rilateral in  form  and  the  angles  are  represented  by  processes.  The 
femporal  process  is  broad  and  is  posteriorly  directed.  The  fronto- 
sphenoidal  process  is  the  most  prominent  and  is  superiorly  directed. 
The  marginal  process  is  anterior  and  somewhat  curved.  The  in- 
ferior process  is  the  least  marked.  The  margins  connecting  these 
processes  are  mostly  thin  and  sharp.  The  temporal  margin  has  a 
projection,  the  processus  marginalis,  and  with  the  orbital  and  masset- 
eric margins  is  free.  To  the  latter  is  attached  the  m.  masseter. 
The  maxillary  margin  is  articular. 

The  medial  surface  is  divided  by  the  orbital  process  which  sepa- 


THE    MANDIBLE 


rates  the  concave  infratemporal  from  the  orbital  areas  (also  called 
surfaces).  Part  of  the  orbital  process  is  nonarticular  and  forms  the 
anterior  boundary  of  the  inferior  orbital  fissure.  The  orbital  area 
of  the  medial  surface  exhibits  two  foramina  (zygomaticoorbitale)  one 
of  which  is  the  internal  opening  of  the  zygomaticofacial  canal  (for 
the  zygomaticofacial  branch  of  the  zygomatic  nerve) ;  the  other  is 
the  zygomaticotemporal  canal  (for  the  zygomaticotemporal  nerve). 
The  former  canal  opens  upon  the  lateral  surface  of  the  bone  and  the 
latter  in  the  temporal  fossa. 


Fig.  43. — The  right  i 
from  the  lateral  surfac 
McMurrich.) 


ar  bones  seen 
(Sobotta    and 


Fig.  44. — The  right  malar  bone  seen 
from  the  media!  or  temporal  surface. 
(Sobotta  and    Sdciiurrich.) 


Articulations. — With  the  temporal,  frontal,  sphenoidal  and  maxillary  bones 
(four). 

Ossification. — It  is  of  intramembranous  origin  and  is  developed  from  three 
centers.  The  center  for  the  orbital  portion  appears  about  the  eighth  to  the  tenth 
week  and  forms  the  bulk  of  the  body  and  the  temporal  process;  a  second  center 
forms  the  temporal  fossa  part  of  the  body  and  the  third  forms  the  lower  part  of 
the  body.  These  fuse  at  about  the  fifth  month  of  fetal  life  but  sutures  may  persist 
between  these  throughout  life. 

Muscle  Attached. — Mm.  caput  infraorbitale,  zygomaticus,  caput  zygomaticum 
and  masse  ter  (foun. 

THE  MANDIBLE  (MANDIBULA) 

The  mandible  is  V-shaped  with  its  extremities  turned  upward. 
It  constitutes  the  entire  lower  jaw  and  is  the  strongest  bone  of  the 
face.     It  supports  the  lower  teeth  and  consists  of  a  body  and  two  rami. 

The  body  (corpus  mandibular)  has  two  surfaces  and  two  margins. 
The  lateral  surface  is  convex  from  side  to  side  and  concave  from  above 
downward.  In  the  median  line  is  a  vertical  ridge,  the  symphysis, 
below  which  is  the  mental  protuberance  (protuberantia  mentalis)  which 
is  divided  into  two  tubercles  (tubera  mentalia).  The  sockets  of  the 
front  teeth  project  somewhat.  At  each  side  of  the  symphysis  is  the 
incisor  fossa  and  in  line  with  the  second  premolar  tooth  is  the  mental 
foramen,  for  the  mental  nerve  and  vessels.  The  oblique  line  (linea 
obliqua)  extends  upward  and  backward  from  the  mental  tubercle. 
The  medial  surface  is  convex  from  above  downward  and  concave 


66 


OSTEOLOGY 


from  side  to  side.  Upon  each  side  of  the  median  line  are  the  menial 
spines  (spina  mentales)  the  upper  giving  attachment  to  the  mm. 
genioglossus  and  the  lower  to  the  geniohyoideus.  Above  the  spine 
is  a  nutrient  foramen.  Below  and  to  the  side  is  the  digastric  fossa 
(fossa  digastrica)  for  the  attachment  of  the  anterior  belly  of  the  m. 
digastricus.  This  surface  is  traversed  and  divided  by  an  oblique 
line  below  and  in  front  over  the  digastric  fossa.  This  is  the  mylo- 
hyoid line  (linea  mylohyoidea)  to  which  the  mm.  mylohyoideus  and 
constrictor  pharyngeus  superior  are  attached.     The  bone  below  this 

Notch  of  the  mandibte 

Pterygoid  depression 

Mead  of  condyloid  process 


Mental  foramen 
Fig.  45. — The  mandible  ! 


Angle  {masseteric  tttbovsityt 


.  from  the  lateral  surface.      (Sobotta  and  McMurrich.) 


line  is  hollow  (fossa  submaxillar  is)  for  the  submaxillary  gland  and  in 
front  is  another  hollow  area  the  fossa  sublingualis. 

The  superior,  or  alveolar  margin,  supports  the  lower  teeth.  The 
inferior  margin  (basis  mandibulce)  is  thicker  than  at  the  junction  of 
the  alveolar  margin  and  the  body.  This  margin  is  longer  than  the 
superior,  rounded  and  grooved  near  the  junction  with  the  ramus  for 
the  external  maxillary  artery. 

The  rami  (rami  mandibulae)  are  flat  and  nearly  vertical  in  direc- 
tion. The  lateral  surface  of  each  is  smooth  but  uneven  due  to  ridges 
for  muscle  attachment  (masseter).  The  medial  surface  is  smooth 
and  irregular.  Near  the  middle  is  the  foramen  mandibular e  that 
leads  into  the  inferior  alveolar  canal  (for  the  vessels  and  nerves  of  the 
same  name).  The  shelf  of  bone  overhanging  the  opening  is  the 
lingula  mandibulce.  An  oblique  groove  (sulcus  mylohyoideus)  extends 
downward  from  the  foramen  lodges  the  mylohyoid  artery  and  nerve. 
The  angle  (angulus  mandibulce)  represents  the  junction  of  the  base  and 
rami.  The  anterior  margin  is  free  and  continuous  with  the  oblique 
line.     The  posterior  margin  is  thick,  smooth  and  covered  by  the  paro- 


THE    SKULL    AS    A    WHOLE 


67 


ticl  gland.  The  inferior  margin  represents  the  fusion  of  ramus  and 
body.  The  superior  margin  is  thin  and  presents  the  coronoid  and 
condyloid  processes  with  an  intervening  mandibular  notch  (incisura 
mandibular). 

The  coronoid  process  {processus  coronoideus)  is  a  flat  triangular  proc- 
ess that  affords  attachment,  laterally,  to  the  mm.  masseter  and 
temporalis,  and  medially  to  the  m.  temporalis.  The  condyloid 
process  (processus  condyloideus)  is  more  massive  and  presents  a 
condyle  and  a  neck.  The  condyle  (capitulum  mandibular)  is  oblong 
with  its  long  axis  transversely  placed.     Its  surface  is  convex  and 


Mental  Spine  Sublingual 

depression 

One-half  of  the  mandibl. 


Mylohyoid  groov, 
Submaxillary  depression 


1  from  the  medial  surface.      (Sobotta  and  McMurrich.) 


mainly  articular.  The  neck  (collum  mandibular)  is  flattened  from 
before  backward  and  ridged.  Upon  its  medial  surface,  anteriorly, 
there  is  a  deep  depression  {fovea  pterygoidea)  for  insertion  of  the  m. 
pterygoideus  medialis. 

Articulations. — With  the  temporal  bones  (two). 

Ossification. — It  is  of  intramembranous  origin  and  develops  from  two  centers, 
one  for  each  half.  These  centers  appear  about  the  forty-fifth  day  of  fetal  life. 
At  birth  the  mandible  consists  of  two  halves  that  fuse,  usually,  by  the  end  of  the 
first  year. 

Muscles  Attached. — The  mm.  mentalis,  quadratus  labii  inferioris,  triangularis, 
platysma,  buccinator,  masseter,  orbicularis  oris,  geniohyoglossus,  geniohyoideus, 
mylohyoideus,  digastricus,  constrictor  pharyngeus  superior,  temporalis  and 
pterygoidei  medialis  and  lateralis  (sixteen  pairs). 

THE  SKULL  AS  A  WHOLE 

Only  a  general  description  of  the  skull  in  various  views  will  be 
given,  as  frontal,  lateral,  occipital,  basal,  medial  and  internal. 

The  frontal  aspect  {norma  frontalis)  exhibits  the  following  impor- 
tant features  for  consideration:  The  frontal  region,  the  orbital  fossa, 
pyriform  aperture  and  dental  arches. 


68 


OSTEOLOGV 


The  frontal  region,  above  the  level  of  the  orbits,  is  convex  in  both 
directions  and  its  breadth  and  height  vary  in  the  different  races. 
The  lower  border  is  sharply  outlined,  on  each  side,  by  the  supraorbi- 
tal margins,  each  of  which  shows  the  supraorbital  notch  (incisura 
supraorbitalis).  In  the  median  line,  near  the  lower  margin  is  the 
and  passing  to  each  side  from  this  are  the  superciliary  arches. 


Fig.   47.— The  skul!  seen  from  in  front.      (Sobotta  anil  McMwrich.) 

The  lateral  borders  of  the  frontal  region  are  sharp,  below,  but  not 
above;  no  superior  border  is  present  as  the  curve  of  the  bone  blends 
with  the  vertex. 

The  orbital  fossae  (two)  are  pyramidal  in  shape  with  the  base 
(orbital  aperture)  at  the  face  and  the  apex  directed  backward  and 
medially.  The  apex  is  practically  the  optic  foramen  (for  the  optic 
nerve  and  ophthalmic  artery);  below  and  medial  to  this  is  the 
superior  orbital  fissure,  for  the  oculomotor,  trochlear,  ophthalmic 
division  of  the  trigeminal,  and  the  abducens  nerves  and  the  ophthal- 
mic veins.  In  the  temporal  part  of  the  orbit  is  the  fossa  for  the  lacri- 
mal gland.     The  roof  is  formed  by  the  orbital  portion  of  the  frontal 


THE    SKULL    AS    A    WHOLE  69 

bone  and  the  small  wing  of  the  sphenoid.  The  floor  is  formed  by  the 
orbital  surfaces  of  the  maxilla  and  zygomatic  bones  and  the  orbital 
process  of  the  palatal  bone.  Here  is  seen  the  inferior  orbital  fissure 
that  transmits  the  maxillary  division  of  the  trigeminal  nerve,  the 
zygomatic  branch  of  that  division,  the  infraorbital  vessels  and  some 
branches  from  the  palatine  ganglion.  Through  the  floor  passes  the 
infraorbital  canal.  The  lateral  wall  is  formed  by  the  great  wing  of 
the  sphenoid  and  the  orbital  surface  of  the  zygomatic  bone.  It  is 
bounded  by  the  two  orbital  fissures,  behind.  In  it  are  seen  two  open- 
ings, the  foramina  zygomaticoorbitalis,  for  the  transmission  of  the 
zygomaticofacial  and  zygomaticotemporal  nerves  from  the  maxillary 
division  of  the  trigeminal  nerve.  The  medial  wall  is  formed  by  the 
frontal  process  of  the  maxilla,  the  lamina  papyracea  of  the  ethmoid 
and  the  body  of  the  sphenoid  bones.  '  At  the  inferior  and  medial 
part  (in  front)  is  seen  the  fossa  for  the  lacrimal  sac. 

The  pyriform  aperture  {aperture  pyriformis)  lies  below  and  between 
the  orbits  and  varies  in  the  different  races.  It  is  bounded  by  the  nasal 
bones  and  the  frontal  processes  of  the  maxillae.  In  the  medial  line 
is  seen  the  anterior  nasal  spine  and,  deeper  in,  the  vomer.  The 
middle  and  inferior  concha?  are  seen  upon  each  lateral  wall. 

The  dental  arches  are  transversely  placed  and  the  upper  overlaps 
the  lower,  slightly.  In  the  mandible,  on  each  side  of  the  midline,  is 
seen  the  mental  foramen  for  the  transmission  of  the  mental  vessels 
and  nerves. 

The  lateral  aspect  (norma  lateralis)  is  mainly  cranial.  This  por- 
tion is  bounded  by  the  frontal,  temporal,  parietal  and  occipital  bones, 
and  lies  above  a  line  drawn  from  the  tip  of  the  mastoid  process  to  the 
nasofrontal  suture.  The  temporal  fossa  lies  above  the  level  of  the 
zygomatic  process  and  extends  upward  to  the  superior  temporal  line. 
The  fossa  contains  the  m.  temporalis,  with  its  nerves,  vessels  and 
fascia,  and  the  zygomaticotemporal  nerve.  Below  the  level  of  the 
zygomatic  arch  the  temporal  fossa  continues  as  the  infratemporal 
fossa,  under  cover  of  the  ramus  of  the  mandible.  Into  this  fossa  open 
the  foramina  ovale  and  spinosum  which  are  best  seen  on  the  basal 
view.  Under  the  root  of  the  zygomatic  arch  is  the  mandibular  fossa, 
for  the  condyle  of  the  mandible,  and  behind  this  is  the  external 
auditory  meatus.  The  pterygopalatine  fossa  is  small  and  somewhat 
hidden.  It  lies  between  the  maxilla,  in  front,  and  the  root  of  the 
pterygoid  process,  behind.  It  communicates  with  the  infratemporal 
fossa  through  the  pterygomaxillary  fissure. 

The  occipital  aspect  (norma  occipitalis)  is  formed  by  the  squamous 
portion  of  the  occipital  bone  and  the  lower  part  of  each  parietal  bone. 
Its  lower  limit  is  the  superior  curved  line  and  in  the  middle  of  this  is 
the  external  occipital  protuberance,  or  inion. 

The  vertex  (norma  verticalis)  is  the  superior  aspect  of  the  skull 


7° 


OSTEOLOGY 


and  varies  greatly.  The  sutures  are  quite  pronounced.  In  the 
midline  is  the  sagittal  suture  between  the  parietal  bones.  This  joins 
the  lamboidal  suture,  between  the  occipital  and  parietal  bones,  be- 
hind. This  junction  indicates  the  posterior  fontanelle  of  the  fetus. 
In  front,  the  sagittal  suture  meets  the  coronal  suture,  between  the 
parietal  and  frontal  bones.  This  junction  corresponds  to  the 
anterior  fontanelle  of  the  fetus. 

The  basalar  aspect  (norma  basalts),  with  the  mandible  off,  is  quite 
complicated.  In  front  are  seen  the  superior  dental  arch  and  the  hard 
palate  with  its  foramen  incisivum.  Back  of  the  hard  palate  are' the 
choanal,  or  posterior  nares  to  the  side  of  which  are  the  pterygoid  and 


vertex 


^     jm  Occiput 


scaphoid  fossce.  At  about  the  middle  of  the  base  is  seen  the  foramen 
magnum  (for  the  spinal  cord  and  vertebral  arteries)  with  the  two  con- 
dyles and  condyloid  foramina  (for  the  hypoglossal  nerve)  at  each  side. 
Back  of  the  foramen  magnum  is  the  external  occipital  crest  with  the 
external  occipital  protuberance  at  its  superior  end,  from  the  latter 
the  superior  nuchal  lines  extend  laterally. 

Lateral  to  the  midline  the  following  are  seen,  from  before  back- 
ward: The  infraorbital  fissure,  the  infratemporal  fossa,  foramen  ovale 
(for  mandibular  branch  of  the  trigeminal  nerve)  for.  spinosum  (for 
middle  meningeal  artery  and  vein)  and  the  mandibular  fossa;  the  fora- 


THE    SKULLL   AS   A   WHOLE  7 1 

men  lacerum  (for  the  carotid  artery  and  great  superficial  petrosal 
nerve),  the  auditory  tube,  the  carotid  canal,  the  jugular  foramen  (for 
the  jugular  vein  and  the  glossopharyngeal,  vagal  and  hypoglossal 
nerves),  the  styloid  process  and  the  external  auditory  meatus;  the 
stylomastoid  foramen  (for  the  facial  nerve),  the  mastoid  notch,  the 
mastoid  process  and  the  mastoid  foramen. 

The  basis  cranii  interna  is  exposed  by  removing  the  vault  of  the 
cranium.  Three  fossae,  anterior,  middle  and  posterior  are  then  seen. 
The  anterior,  the  smallest,  lies  at  the  highest  level.  It  is  bounded, 
in  front,  by  the  vertical  portion  of  the  frontal  bone  and  behind,  by  the 
edges  of  the  small  wings  of  the  sphenoid  bone.  In  the  middle  are 
seen  the  foramen  cecum  and  the  crista  galli;  at  the  sides  of  the  latter 
are  the  olfactory  grooves  (for  the  olfactory  lobes)  and  the  cribriform 
plate,  of  the  ethmoid.  This  plate  is  pierced  for  the  transmission  of 
the  olfactory  nerves.  The  frontal  lobes  of  the  cerebrum  lie  in  this 
fossa. 

The  middle  fossa  lies  between  the  edges  of  the  small  wings  of  the 
sphenoid  bone  and  the  superior  margins  of  the  petrous  portions  of  the 
two  temporal  bones.  This  is  narrow  in  the  midline  and  here  is  seen 
the  pituitary  fossa  for  lodgment  of  the  pituitary  gland.  This  fossa 
contains  in  addition  the  cruri  cerebri  and  the  temporal  lobes  of  the 
cerebrum.  At  each  side,  and  from  before  backward,  are  the  optic 
foramen,  internal  opening  of  the  carotid  canal,  and  the  carotid  groove. 
Far  to  the  side  the  foramina  rotundum,  ovale,  spinosum  and  lacerum, 
the  depression  for  the  semilunar  ganglion  and  the  hiatus  facialis. 
The  superior  orbital  fissure  is  here  but  it  is  hidden  by  the  overhang- 
ing posterior  edge  of  the  small  wing  of  the  sphenoid. 

The  posterior  fossa  is  the  largest,  deepest  and  at  the  lowest  level. 
It  contains  the  cerebellum.  It  lies  between  the  superior  margins 
of  the  petrous  portions  of  the  two  temporal  bones,  in  front,  and  the 
vertical  portion  of  the  occipital  bone,  behind.  It  is  roofed  over  by 
the  tentorium  cerebelli.  In  the  midline  are  the  foramen  magnum 
with  the  canal  is  hypoglossi  upon  each  side;  then  follow  the  internal 
occipital  crest  and  internal  occipital  protuberance.  At  the  sides  of  the 
midline  are  seen  the  internal  acoustic  meatus,  the  jugular  foramen  and 
grooves  for  the  superior  and  inferior  petrosal  sinuses  and  the  lateral 
and  sigmoid  sinuses. 

In  a  median  sagittal  section  of  the  skull,  the  bulk  is  represented 
by  the  cavity  of  the  cranium,  for  the  brain.  In  the  frontal  bone  is 
seen  the  frontal  sinus;  within  the  body  of  the  sphenoid  is  the  sphe- 
noidal sinus  and  in  the  superior  surface  of  the  body  is  the  pituitary 
fossa.  In  the  posterior  fossa  is  the  internal  acoustic  meatus.  The 
facial  portion  of  this  section  presents  the  nasal  cavity  (cavum  nasi). 
This  and  its  connections  are  described  on  page  271. 

At  birth  the  facial  portion  of  the  skull  represents  only  about  one- 


72  OSTEOLOGY 

eighth  the  mass  of  the  cranial  portion.  The  median  line  junction  of 
the  frontal  and  parietal  bones  is  incomplete,  constituting  the  frontal 
fontanelle  (fonliculus  frontalis);  this  is  diamond-shaped,  covered  in  by 
membrane  and  is  closed  by  bone  by  about  the  middle  of  the  second 
year.  Between -the  parietal  and  occipital  bones  there  is  also  an  area 
where  the  bones  are  incomplete  and  this  is  the  posterior  fontanelle 
(fonticulis  occipitalis).  This  is  closed  usually  by  the  second  month 
after  birth.  Lateral  fontanelles  are  usually  present  at  the  sphenoidal 
angles  of  the  parietal  bones.  The  parietal  eminences  are  unusually 
prominent  at  birth  and  represent  the  less-marked  tubera  parietalia 
of  the  adult. 

The  forehead  bulges  prominently  at  the  regions  of  the  frontal 


Frontal  fontanelle 


Frontal  eminence 


Sphenoid  fontanelle 

Occipital  fontanelle 


Parietal  eminence 


Fig.  49. — Skull  of  a  new-born  child  seen  from  the  left  side.     (Sobolla  and  McMurrich.) 

tuberosities.  The  apertura  pyriformis  is  relatively  wider  than  in  the 
adult,  the  maxilla?  are  low  and  the  alveolar  margins  poorly  marked. 
The  maxillary  sinus  is  merely  indicated  by  a  groove.  The  mastoid 
process  is  barely  noticeable.  The  mandible  consists  of  lateral  halves 
united  by  fibrous  tissue  and  the  alveolar  margin  is  poorly  marked. 
The  ramus  is  wide  and  the  angle  is  obtuse. 

In  the  adult  the  face  constitutes  about  one-half  of  the  mass  of  the 
cranium.  This  is  mainly  due  to  the  eruption  of  the  teeth  and  the 
development  of  the  air  sinuses. 

As  regards  sex,  the  skull  of  the  average  female  is  smaller  than  that 
of  the  average  male  by  about  one-tenth.  It  is  lighter,  smoother  and 
less  well  marked  in  regard  to  ridges  for  muscle  attachment.  The 
forehead  is  usually  more  vertical  though  the  frontal  and  occipital 


THK    CLAVICLE 


73 


regions  are  less  capacious 
more  oval. 


The  vertex  is  usuallv  flatter  and  the  face 


BONES   OF  THE  SUPERIOR   ( PECTORAL )   EXTREMITY 

The  bones  of  each  pectoral  appendage  are  the  clavicle,  scapula  (form- 
ing one-half  of  the  shoulder  girdle)  the  humerus  (arm),  the  radius  and 
ulna  (forearm),  carpal  bones  (wrist),  metacarpal  bones  (palm)  and 
the  phalanges  (fingers). 

THE  CLAVICLE 

The  clavicle,  or  collar  bone,  is  a  ~-shaped  bone  that  forms  the 
ventral  portion  of  the  pectoral  girdle  on  each  side.  It  consists  of  a 
shaft  and  two  extremities. 


(.Subotta  and  McMurrich.) 


The  sternal  extremity  (ertremitas  sternalis)  is  enlarged,  oval  and 
somewhat  concave,  from  above  downward.  Its  articular  surface  is 
smooth,  and  articulate  with  the  manubrium  sterni;  from  this  bone, 
however,  it  is  separated  by  the  interarticular  fibrocartilage.  This 
extremity  also  rests  upon  the  first  costal  cartilage.  The  edge  of  the 
articular  area  serves  for  the  attachment  of  the  capsular  ligament. 

The  shaft  has  a  double  curve.     The  sternal  two-thirds  is  cylindrical 


'Sternal  articular    — 
tuberosity 


[Sobotta  ami  McMurrich. 


and  convex  in  front,  and  the  acromial  one-third  is  flattened  and  con- 
cave in  front.  The  shaft  has  two  surfaces  and  two  margins.  The 
superior  surface  is  smooth  and  subcutaneous.  The  inferior  surface 
shows,  near  the  sternal  extremity,  a  depression  (tuberositas  costalis) 
for  the  attachment  of  the  costoclavicular  ligament.  Beyond  this  a 
groove  extends  to  the  acromial  extremity  and  here  the  m.  subclavius 
is  inserted.  The  ventral,  or  anterior  margin,  is  roughened  and  from 
its  sternal  portion  arises  the  clavicular  part  of  the  m.  pectoralis 
major;  from  its  acromial  end  a  portion  of  the  m.  deltoideus  arises. 


74  OSTEOLOGY 

The  dorsal,  or  posterior  margin  is  broad  at  its  sternal  end  and  here  the 
clavicular  portion  of  the  m.  sternomastoideus  arises;  immediately 
below  this  the  m.  sternohyoideus  has  its  origin.  Near  the  acromial 
end  of  this  margin  is  a  small  projection,  the  coracoid  process  {tuber- 
ositas coracoidea)  for  attachment  of  the  conoid  ligament. 

The  acromial  extremity  presents,  at  its  end,  an  oval  facet  for 
articulation  with  the  acromion  of  the  scapula;  to  the  edges  of  this 
area  is  attached  the  capsular  ligament.  Its  superior  surface  is 
roughened  and  mainly  subcutaneous.  The  inferior  surface  shows 
the  oblique  trapezoid  ridge  at  the  dorsal  end  of  which  is  the  tuberositas 
coracoidea.  These  are  for  the  attachment  of  the  trapezoid  and 
conoid  portions  of  the  coracoclavicular  ligament,  respectively. 
The  ventral,  or  anterior  margin  is  thin  and  gives  origin  to  the  m. 
deltoideus.  The  dorsal,  or  posterior  margin  is  roughened  for  the 
insertion  of  the  m.  trapezius. 

The  nutrient  foramina  are  large  and  on  the  dorsal  margin. 

Articulations. — With  the  scapula  and  sternum  (indirectly). 

Ossification. — It  is  endochondral  in  origin  and  develops  from  ti,o  centers,  one 
for  the  shaft  and  acromial  extremity  (fifth  to  sixth  week)  and  one  for  the  sternal 
extremity  (fifteenth  to  twentieth  year).  It  is  the  first  bone  to  ossify  and  fusion  of 
the  two  parts  is  completed  by  about  the  twenty-fifth  year. 

Muscles  Attached. — Origins. — Mm.  sternomastoideus,  deltoideus,  pectoralis 
major,  and  sternohyoideus.     Insertions. — 11m.  trapezius  and  subclavius  (six). 

THE  SCAPULA 

The  scapula,  or  shoulder  blade  forms  the  dorsal  half  of  the  pectoral 
girdle  on  each  side.  It  is  flat,  somewhat  triangular  and  presents 
a  body,  a  spine  and  two  processes. 

The  body  is  triangular  and  thin  and  presents  two  surfaces,  three 
margins  and  three  angles.  The  ventral,  or  costal  sulfate  {fades 
costalis)  is  concave  in  both  directions  and  forms  a  fossa.  Along 
its  medial,  or  vertebra!  margin  the  m.  serratus  anterior  is  inserted. 
The  superior  half  of  the  lateral,  or  axillary  margin  is  thick  deepen- 
ing the  fossa  in  this  area.  The  surface  of  the  bone  shows  several 
ridges  that  converge  toward  the  neck.  The  fossa  and  ridges  give 
origin  to  the  m.  subscapularis. 

The  dorsal  surface  (fades  dorsalis)  is  crossed,  almost  horizontally, 
by  the  spine,  which  divides  this  surface  into  two  portions  or  fossa?. 
The  upper,  smaller  supraspinous  fossa  is  above  the  spine  and  the 
latter  forms  its  floor.  From  the  outer  part  arises  the  m.  supra- 
spinatus.  This  fossa  communicates  with  the  infraspinous  fossa 
by  means  of  the  great  scapular  notch  that  transmits  the  transverse 
scapular  artery  and  suprascapular  nerve.  The  infraspinous  fossa 
is  triangular  and  roofed  by  the  inferior  surface  of  the  spine.  The 
bulk  of  this  area  gives  origin  to  the  m.  infraspinatus.  Along  the 
vertebral   margin   the  m.  rhomboidei   is  inserted;  along  the  upper 


THE   SCAPULA 


75 


Acromion 
Glenoid  cavity 

' 

External 

Neck 

Axillary  bordt 

Inferior  angle 
Fig.  52. — The  dorsal  surface  of  the  left  scapula.     (Sobotta  and  McMurrich.) 


Subscapular  ft 
Internal  angle 


Acromion       Articular  surface  of 
Coracoid 


Inferior  angle 
PlC.   53. — The  costal  surface  of  the  left  scapula.      (Sobotta  and  McMurrich.) 


76  OSTEOLOGY 

two-thirds  of  the  axillary  margin  the  m.  teres  major  arises  while 
from  the  lower  third  the  m.  teres  minor  takes  origin.  Occasionally 
the  m.  latissimus  dorsi  has  an  origin  at  the  inferior  angle. 

The  superior  margin  is  thin,  sharp  and  presents  the  scapular 
notch.  Usually  this  notch  is  bridged  by  a  ligament  and  through 
the  foramen  thus  formed  passes  the  suprascapular  nerve  while 
above  the  ligament  courses  the  transverse  scapular  artery.  The 
posterior  belly  of  the  m.  omohyoideus  arises  near  the  notch.  The 
vertebral  margin  (margo  vertebralis)  is  the  longest.  It  is  irregular 
and  to  it  are  inserted  the  mm.  levator  scapulae,  and  rhomboideus 
major  et  minor  (from  above  downward).  The  axillary  margin  is 
thick.  The  part  just  below  the  glenoid  fossa  is  roughened  (tuberositas 
infraglenoidalis)  and  from  this  arises  the  long  head  of  the  m.  triceps. 

The  angles  are  medial,  inferior  and  lateral.  The  medial  and  in- 
ferior angles  are  rather  blunt.  The  lateral  angle,  occasionally  called 
the  head,  supports  the  glenoid  cavity  and  coracoid  process.  The 
glenoid  cavity  is  oval  and  concave  in  both  directions;  its  edge  affords 
attachment  to  the  capsular  ligament.  Below  the  cavity  is  the  infra- 
glenoid  tuberosity  and  above  is  the  supraglenoid  tubercle  (tuberositas 
supraglenoidialis)  from  which  arises  the  long  head  of  the  m.  biceps 
brachii.  The  neck  (collum  scapula)  connects  the  glenoid  cavity 
to  the  body.  It  is  constricted  and  is  indicated  by  a  line  connecting 
the  scapular  notch  and  the  infraglenoid  tuberosity. 

The  spine  (spina  scapula)  is  on  the  dorsal  surface  and  arises  near 
the  vertebral  margin  and  passes  obliquely  upward  and  laterally 
toward  the  glenoid  cavity;  here  the  spine  twists  and  leaves  the  dorsal 
surface  to  form  a  free  projecting  mass  of  bone  called  the  acromion. 
At  its  glenoid  edge  it  forms  the  great  scapular  notch.  The  main 
part  of  the  spine  separates  the  supra-  and  infraspinous  fossae,  from 
each  other.  Its  ventral  margin  is  fused  to  the  body  of  the  bone 
while  its  dorsal  margin  is  free  and  subcutaneous;  to  the  upper  lip  of 
this  margin  the  m.  trapezius  is  inserted  and  from  the  inferior  lip  the 
m.  deltoideus  arises. 

The  acromion,  one  of  the  processes,  is  a  continuation  of  the  spine. 
It  is  flattened  from  above  downward  and  overhangs  the  glenoid 
cavity.  It  presents  superior  and  inferior  surfaces  and  medial  and 
lateral  margins.  The  superior  surface  slopes  upward,  faces  dorsally 
and  is  subcutaneous.  The  inferior  surface  is  smooth.  The  medial 
margin  presents  a  facet  (facies  articularis  acromii)  for  articulation 
with  the  acromial  extremity  of  the  clavicle.  The  m.  trapezius  is 
inserted  to  the  medial  margin  while  the  m.  deltoideus  arises  from  the 
lateral  margin. 

The  coracoid  process  (processus  coracoideus)  is  attached  to  the 
upper  part  of  the  head  just  lateral  to  the  scapular  notch.  It  is  bent 
in  such  a  manner  so  as  to  overhang  the  glenoid  cavity.     To  the 


THE  HUMERUS  77 

upper  surface,  near  the  bend,  are  attached  the  trapezoid  and  conoid 
ligaments.  Its  dorsal  margin  affords  attachment  to  the  coraco- 
acromial  ligament  and  near  its  apex  the  m.  pectoralis  minor  is  in- 
serted. From  the  apex  the  mm.  coracobrachialis  and  short  head  of 
the  biceps  arise. 

Nutrient  foramina  are  numerous  around  the  glenoid  cavity  and  upon  the 
surfaces  of  the  spine. 

Articulations. — With  the  clavicle  and  humerus  (two). 

Ossification. — It  is  of  endochondral  origin  and  is  developed  from  seven 
centers.  The  center  for  the  body  appears  about  the  seventh  to  eighth  week  of 
fetal  life;  two  centers  appear  for  the  coracoid  process,  one  during  the  first  year  and 
the  other  about  the  tenth  year;  two  centers  appear  for  the  acromion  at  about  the 
age  of  puberty;  one  center  appears  for  the  inferior  angle  about  the  sixteenth  year 
and  one  for  the  vertebral  margin  at  about  the  seventeenth  year.  All  parts  are 
usually  fused  by  the  twenty-fifth  year. 

Muscles  Attached. — Origin. — Mm.  subscapularis,  omohyoideus,  supraspinatus, 
infraspinatus,  teres  major,  teres  minor,  deltoideus,  coracobrachialis,  long  head  of 
the  triceps,  short  head  of  the  biceps  and  occasionally  the  latissimus  dorsi. 

Insertions. — Mm.  trapezius,  levator  scapulae,  rhomboidei  major  et  minor, 
serratus  anterior  and  pectoralis  minor  (seventeen). 

THE  HUMERUS 

The  humerus  constitutes  the  support  of  the  arm  muscles.  It  con- 
sists of  a  proximal  extremity,  a  shaft  and  a  distal  extremity. 

The  proximal  extremity  comprises  the  head,  neck  and  two  tubercles. 
The  head  {caput  humeri)  forms  about  one-third  of  a  sphere  and  is 
articular,  resting  in  the  glenoid  cavity  of  the  scapula.  Its  dorsal 
half  is  the  more  convex,  and  the  whole  surface  faces  medially  and 
somewhat  upward  and  dorsallv.  It  is  set  off  from  the  rest  of  the 
bone  by  a  constriction,  the  anatomical  neck  (collum  anatomicum)  to 
which  the  capsular  ligament  is  attached.  The  tubercles  are  large  and 
small.  The  larger  (tuberculum  majus)  seems  to  be  a  projection  of 
the  shaft  and  presents  three  facets  for  the  insertion  of  the  mm.  supra- 
spinatus, infraspinatus  and  teres  minor  (from  above  downward). 
It  has  numerous  nutrient  foramina.  The  smaller  tubercle  (tuberculum 
minor)  is  attached  to  the  front  of  the  proximal  extremity  and  is 
separated  from  the  preceding  by  the  bicipital  groove  (sulcus  inter- 
tuber  cularis).  The  two  tubercles  are  connected  by  the  transverse 
humeral  ligament.  To  the  small  tubercle  the  m.  subscapularis  is 
inserted.  The  part  of  the  bone  succeeding  these  parts  is  the  surgical 
neck  (collum  chirurgicum)  and  is  the  part  most  liable  to  fracture. 

The  shaft  (corpus  humeri)  is  partly  cylindrical  and  partly  flattened 
(distally).  It  presents  ventral  and  dorsal  surfaces  and  medial  and 
lateral  margins.  The  proximal  half  of  the  ventral  surface  is  divided 
into  lateral  and  medial  portions  by  the  intertubercular  groove.  The 
tips  of  this  groove  are  the  crests  of  the  larger  and  smaller  tubercle; 
(they  are  called   the  crista  tuberculi   majoris   (lateral)  and  minoris 


78 


OSTEOLOGY 


medial).  The  muscles  inserted  here  are  the  mm.  pectoralis  major 
(lateral  lip),  latissimus  dorsi  (floor  of  groove),  teres  major  (medial 
lip).  At  the  end  of  the  lateral  part  of  the  ventral  surface  is  the  V- 
shaped  deltoid  tuberosity  (tuberositas  deltoidea)  for  the  insertion  of  the 
m.  deltoideus.  The  medial  ventral  surface,  near  the  middle  of  the 
shaft,  receives  the  fibers  of  the  m.  coracobrachialis.     The  distal  por- 


Greatcr  tubercle 

Upper 

extremity 


Anatomical  neck 

'ntertubtrntlar  grccrt  t 

.  Greater  tubercle 


Lower 
extre- 
mity 


FIG.   54—  The   left   h 


behind.      (Sobotta   and    MtMurrith.) 


Fig.  S5-— The  left  hu 

front.      {Sobotta  and  AIcAlurrich.) 


tion  of  the  ventral  surface  presents  a  ridge  that  begins  at  the  deltoid 
tubercle  that  forms  two  sloping  surfaces  from  which  the  m.  brachialis 
anterior  arises.  The  dorsal  surface  is  divided  into  proximal  and  distal 
(greater)  portions  by  the  oblique  groove  for  the  radial  nerve  (sulcus 
nervus  radialis).  The  nerve  is  accompanied  by  the  profunda  brachii 
artery.     Its  course  is  downward  and  laterally.     Upon  the  upper 


THE   HUMERUS 


79 


part  there  is  a  ridge  from  which  the  lateral  (small)  head  of  the  m. 
triceps  arises.  Distal  to  the  groove  the  surface  is  smooth,  extensive 
and  gives  origin  to  the  medial  head  of  the  m.  triceps.  The  medial 
margin  {margo  medialis)  is  rounded  and  indistinct,  proximally,  while 
distally  its  prominent  epicondylic  ridgs  ends  at  the  medial  epicondyle. 
At  about  the  middle  of  this  margin  is  seen  the  insertion  of  the  m. 
coracobrachialia.  The  lateral  margin  {margo  lateralis)  is  more 
prominent,  especially  at  its  distal  extremity  where  it  is  grooved  for 
the  radial  nerve  and  the  profunda  brachii  artery.  This  distal  por- 
tion constitutes  the  lateral  epicondylic  ridge  from  which  arise  the 
mm.  brachioradialis  (proximal  two-thirds)  and  extensor  carpi 
radialis  longus  (distal  one-third). 

The  distal  extremity  comprises  the  epicondyles,  trochlea  and  capi- 
tal urn.  The  lateral  epicondyle  (epicondylus  lateralis)  is  small  and 
from  it  arises  the  m.  anconeus  and  the  common  tendon  of  origin 
of  the  extensor  muscles.  The  medial  epicondyle  (condylus  medialis) 
is  more  prominent  and  affords  origin  to  the  m.  pronator  teres  and 
the  superficial  flexor  muscles  of  the  forearm. 

The  trochlea  is  a  spool-shaped  articular  surface  for  the  proximal 
extremity  of  the  ulna.  Its  ventral  surface  is  more  extensive  than 
the  dorsal  surface.  It  is  placed  obliquely  to  the  long  axis  of  the 
bone.  The  coronoid  fossa  (fossa  coronoidea)  is  just  proximal  to  the 
trochlea  on  the  ventral  surface  of  the  bone.  This  receives  the 
coronoid  process  of  the  ulna  during  flexion  of  the  forearm.  In  a 
corresponding  position  upon  the  dorsal  surface  is  the  deeper  ole- 
cranon fossa  (fossa  olecrani)  for  the  reception  of  the  olecranon 
process  of  the  ulna  during  extension  of  the  forearm. 

The  capilulum  is  lateral  to  the  trochlea  and  articulates  with  the 
head  of  the  radius.  It  is  separated  from  the  trochlea  by  a  groove. 
Its  articular  portion  is  rounded  ventrally  and  distally  but  not 
dorsally.  It  is  attached  to  the  ventral  surface  of  the  humerus. 
Just  proximal  to  the  capitullum  is  the  radial  fossa  (fossa  radialis) 
for  the  reception  of  the  head  of  the  radius  during  flexion  of  the 
forearm. 

Nutrient  foramina  are  numerous;  the  two  largest  (distally  directed)  are  near 
the  insertions  of  the  mm.  deltoideus  and  coracobrachialis.  The  smaller  ones 
are  in  the  region  of  the  anatomical  neck. 

Articulations. — With  the  scapula,  radius  and  ulna  (three). 

Ossification.— It  is  of  endochondral  origin  and  is  developed  from  six  centers. 
One  for  the  shaft  appears  during  the  seventh  week  of  fetal  life;  one  for  the  head 
appears  during  the  fifth  or  sixth  month  (postnatal);  one  for  the  large  tubercle 
during  the  second  or  third  year;  one  for  the  small  tubercle  at  the  end  of  the  third 
year.  The  first  three  are  fused  by  the  seventh  year  and  this  epiphysis  is  fused 
with  the  shaft  by  the  twenty-fifth  year.  The  center  for  the  capilulum  and 
lateral  half  of  the  trochlea  appears  during  the  second  or  third  years;  that  for  the 
medial  pari  of  the  trochlea  about  the  sixth  year;  that  for  the  lateral  condyle  about 
the  twelfth  year.  The  medial  condyle  fuses  with  the  shaft  at  about  the  nine- 
teenth year  and  the  others  by  about  the  seventeenth  year. 


80  OSTEOLOGY 

Muscles  Attached. — Origin. — Mm.  triceps,  brachialis,  pronator  teres,  flexor 
carpi  radialis,  palmaris  longus,  flexor  carpi  ulnaris,  flexor  digitorum  sublimis, 
brachioradialis,  extensor  carpi  radialis  longus,  extensor  carpi  radialis  brevis. 
extensor  digitorum  communis,  extensor  digiti  quinti  proprius,  extensor  carpi 
ulnaris,  anconeus  and  supinator  (brevis). 

Insertions. — Mm.  subscapularis,  supraspinatus,  infraspinatus,  teres  minor, 
pectoralis  major,  latissimus  dorsi,  teres  major,  coracobrachialis  and  deltoideus. 

THE  ULNA 

The  ulna  constitutes  the  medial  bone  of  the  forearm  and  consists 
of  a  proximal  extremity,  shaft  and  a  distal  extremity. 

The  proximal  extremity  comprises  the  olecranon  and  coronoid 
processes.  The  olecranon  process  is  a  direct  continuation  of  the 
shaft  and  represents  the  dorsal  part  of  the  extremity.  Its  dorsal 
surface  is  triangular,  covered  with  a  bursa  and  subcutaneous.  The 
superior  (proximal)  surface  is  nearly  at  a  right  angle  with  the  dorsal 
surface  and  forms  at  this  junction  the  tip  of  the  elbow  where  the 
tendon  of  the  m.  triceps  is  inserted.  The  ventral,  or  volar  surface, 
is  smooth  and  concave,  from  above  downward,  and  convex,  from 
side  to  side.  It  articulates  with  the  trochlea  of  the  humerus.  The 
sharp  margin  between  these  two  surfaces  serves  for  attachment  of 
the  ligaments  of  the  elbow  joint. 

The  coronoid  process  (processus  coronoideus)  projects,  shelf-like, 
from  the  ventral  surface  of  the  bone.  The  proximal  surface,  with 
the  ventral  surface  of  the  olecranon,  forms  the  semilunar  notch  for 
articulation  with  the  trochlea  of  the  humerus.  The  ventral  or  volar 
surface  of  the  coronoid  process  is  rough,  triangular  and  continuous 
with  the  corresponding  surface  of  the  shaft.  It  usually  presents 
a  tubercle  (tuberositas  ulna)  for  insertion  of  the  tendon  of  the  m. 
brachialis.  The  margin  affords  attachment  to  ligaments  of  the 
elbow  joint.  The  ventral  surface  also  affords  origin  to  the  mm. 
flexor  digitorum  sublimis  and  pronator  teres  and  occasionally  to  the 
flexor  pollicis  longus. 

The  semilunar  notch  {incisura  semilunaris)  articulates  with  the 
trochlea  of  the  humerus.  This  notch  is  narrowest  across  the 
middle  and  is  uneven  so  as  to  approximate  closely  to  the  trochlear 
surface. 

The  radial  notch  (incisura  radialis)  is  at  the  lateral  margin  of  the 
coronoid  process.  It  is  concave  dorsoventrally  and  comparatively 
small,  accommodating  the  head  of  the  radius.  Medially  it  joins 
the  semilunar  notch  and  all  of  its  other  margins  serve  for  attachment 
of  ligaments. 

The  shaft  (corpus  ulna)  is  tapering  and  its  distal  extremity  is 
slightly  curved,  laterally.  It  presents  three  surfaces  and  three 
margins.  The  ventral,  or  volar  surface,  is  smooth  and  concavo- 
convex.     It  affords  origin  for  the  mm.  supinator,  flexor  digitorum 


THE  ULNA  » I 

profundus,  pronator  teres  and  pronator  quadratus  (from  above 
downward).  The  medial  surface  is  smooth  and  not  sharply  defined 
from  the  ventral  surface;  it  affords  origin  to  the  m.  flexor  digitorum 
profundus  and  is  often  described  with  the  ventral  surface.  The 
dorsal  surface  is  quite  well  defined  and  faces  somewhat  laterally. 


Dorsal  border 
Internal  stir/the 


Fig.  56.— The  left  ulna  seen  from  be- 
hind.    (Sobolta  ami  McMurrich.) 


Fig.  57. — The  left  ulna  seen  from  ; 
front.     (Sobolta  and  McMurrich.) 


It  is  smooth  and  concave  in  its  proximal  two-thirds  and  the  distal 
portion  is  rounded  and  not  sharply  separated  from  the  medial 
surface.  Its  proximal  portion  affords  origin  to  the  mm.  anconeus 
and  then  in  order  (but  along  its  lateral  margin)  the  abductor  pollicis 
longus,  extensor  pollicis  longus  and  extensor  indicis  proprius. 


82  OSTEOLOGY 

The  ventral,  or  volar  margin  is  rounded  extending  from  the  tuber- 
osity to  the  styloid  process  and  affords  origin  to  the  m.  flexor  digito- 
rum  profundus.  The  dorsal  margin  (margo  dorsalis)  is  sharp  and 
subcutaneous.  To  it  is  attached  the  aponeurosis  of  the  mm.  flexor 
carpi  ulnaris,  extensor  carpi  ulnaris  and  flexor  digitorum  profundus. 
The  lateral  margin,  or  interosseous  crest  {crista  interossei),  is  sharp 
and  well  defined  in  its  proximal  three-fourths.  To  almost  its  entire 
extent  it  affords  attachment  to  the  interosseous  membrane. 

The  distal  extremity  comprises  a  head  and  a  styloid  process.  The 
head  (capitulum  ulna:)  in  its  ventrolateral  portion  is  smooth, 
convex,  narrow  and  articulates  with  the  ulnar  notch  of  the  radius. 
Its  distal,  flat,  semilunar  surface  rests  upon  the  interarticular  car- 
tilage of  the  wrist  joint.  The  margin  affords  attachment  to  the 
ligament  that  holds  this  bone  to  the  radius.  The  styloid  process 
is  a  small  projection  of  bone  medial  and  dorsal  to  the  head  from 
which  it  is  separated  by  a  small  groove.  This  groove  extends  upon 
the  dorsal  surface  of  the  bone  and  lodges  the  tendon  of  the  m. 
extensor  carpi  ulnaris. 

Nutrient  foramina  are  numerous.  The  main  ones  (distally  directed)  is  on  the 
ventral  surface  near  the  middle.  Others  are  seen  near  the  radial  notch  and  near 
the  groove  at  the  distal  extremity  of  the  bone. 

Articulations. — With  the  radius  (at  both  ends)  and  the  humerus. 

Ossification. — It  is  of  endochondral  origin  and  develops  from  three  centers. 
The  coiler  for  the  shaft  appears  about  the  eighth  week  of  fetal  life;  that  for  the 
distal  extremity  appears  during  the  fourth  year  (sixth  to  the  eighth  year  (Pryor) 
and  for  the  proximal  extremity  about  the  tenth  year.  The  shaft  and  proximal 
extremity  fuse  about  the  sixteenth  year  and  the  distal  extremity  fuses  with  the 
shaft  at  about  the  twentieth  year. 

Muscles  Attached. — Origin. — Mm.  supinator,  pronator  teres,  flexor  digitorum 
sublimis,  flexor  digitorum  profundus,  pronator  quadratus,  flexor  carpi  ulnaris, 
extensor  carpi  ulnaris,  flexor  pollicis  longus,  extensor  pollicis  brevis,  extensor 
indicis  proprius,  extensor  pollicis  longus. 

Insertions. — Mm.  triceps,  anconeus  and  brachialis  (fourteen). 

THE  RADIUS 

The  radius  is  the  shorter  bone  of  the  forearm  and  is  laterally 
placed.     It  consists  of  a  proximal  extremity,  shaft  and  distal  extremity. 

The  proximal  extremity  comprises  the  head,  neck  and  tuberosity. 
The  head  (capitulum  radii)  is  disc-like  and  its  surface  concave  and 
articular  (fovea  capituli  radii).  Its  margin  is  broad  and  smooth  and 
its  medial  portion  articulates  with  the  radial  notch  of  the  ulna.  The 
remainder  of  the  margin  is  enclosed  by  the  annular  ligament  of  this 
joint.  The  neck  (folium  radii)  is  the  smooth,  constricted  portion 
of  bone  between  the  head  and  shaft.  The  tuberosity  (tuberositas 
radii)  is  an  oval  projection  on  the  medial  and  proximal  part  of  the 
radius.  Its  dorsal  surface  is  roughened  for  the  insertion  of  the 
tendon  of  the  m.  biceps  brachii;  its  ventral  surface  is  smooth  and 
covered  by  a  bursa. 


THE  RADIUS 


83 


The  shaft  {corpus  radii)  is  larger  distally  than  proximally  and  has 
a  lateral  convex  curve.  It  has  three  surfaces  and  one  well-marked 
margin.  The  ventral,  or  volar  surface  is  smooth  and  slightly  convex 
proximally  and  broad  and  flat  distally.  It  is  crossed  by  the  ventral 
oblique  line,  from  which  the  m.  flexor  digitorum  sublimis  takes 
origin,  and  proximal  to  which  the  m.  supinator  is  inserted.  The 
bulk  of  this  surface  gives  origin  to  the  m.  flexor  pollicis  longus; 


Styloid  process 


Styloid  process 


-The  left  radius  seen  from  i 
(Sobolta  and  McMurrich.) 


Fig.  50. — The  left  radius  seen  from  be- 
hind.     (Sobotta  and  McMurrich.) 


to  the  distal  part  the  m.  pronator  quadratus  is  inserted.  The  lateral 
surface  {margin)  is  broader  proximally  than  distally  where  it  is  more 
ridge-like  passing  into  the  base  of  the  styloid  process.  The  m. 
supinator  is  inserted  to  the  proximal  portion  (as  well  as  the  neck); 
the  m.  pronator  teres  to  the  middle  part  and  the  distal  part  is 
covered  by  muscles.    The  dorsal  surface  {fades  dorsalis)  is  broadest  at 


84  OSTEOLOGY 

its  distal  portion  and  narrow  proximally.  It  is  crossed  by  the  dorsal 
oblique  line  proximal  to  which  the  m.  supinator  is  inserted.  Distal 
to  the  line  the  mm.  extensor  pollicis  longus  and  extensor  pollicis 
brevis  respectively  arise.  The  distal  quarter  of  the  surface  is 
subcutaneous  and  has  several  grooves  that  continue  onto  the  ex- 
tremitv.  The  interosseous  crest  (crista  interossei)  is  the  lateral 
margin  and  is  the  only  one  that  is  well  defined.  It  begins  proximally 
at  the  tuberosity  and  distally  divides  to  embrace  the  ulnar  notch 
of  the  distal  extremity.  To  the  triangular  area  so  formed  the  m. 
pronator  quadratus  is  inserted.  The  crest  gives  attachment  to 
the  interosseous  membrane. 

The  distal  extremity  has  two  articular  surfaces  and  a  styloid  process. 
The  distal  surface  (carpal  articular)  is  slightly  concave  and  divided 
into  two  facets.  The  lateral  of  these  surfaces  is  triangular  and  for 
articulation  with  the  navicular  (scaphoid)  and  the  medial  is  quadri- 
lateral and  articulates  with  the  lunate  (semilunar)  bones  of  the 
carpus.  The  concave  ulnar  notch  (incisura  ulnaris)  is  on  the  medial 
margin  of  the  distal  extremity  of  the  head  of  the  radius  and  to  its 
distal  edge  is  attached  the  articular  cartilage  that  supports  the 
head  of  the  ulna  and  prevents  it  from  participating  in  the  formation 
of  the  wrist  joint.  To  the  ventral  and  dorsal  edges  ligaments  are 
attached.  The  ventral  margin  of  the  distal  extremity  gives  attach- 
ment to  the  capsular  ligament  of  the  wrist  Joint.  The  dorsal 
margin  is  irregular  and  grooved  for  tendons  and  also  gives  attach- 
ment to  the  capsular  ligament.  The  broad  medial  groove  contains 
the  tendons  of  the  mm.  extensor  digitorum  communis  and  extensor 
indicis  proprius.  The  next  one  accommodates  the  tendon  of  the 
m.  extensor  pollicis  longus;  the  last  groove  accommodates  the 
tendons  of  the  mm.  extensores  carpi  radialis  longus  and  brevis. 

The  styloid  process  is  the  pointed  projection  of  the  lateral  surface  of 
the  distal  extremity.  The  lateral  surface  of  its  proximal  end  is 
grooved  and  the  tendon  of  the  m.  brachioradialis  is  here  inserted. 
The  remainder  of  the  groove  accommodates  the  tendons  of  the  mm. 
abductor  pollicis  longus  and  extensor  pollicis  brevis.  The  medial 
surface  of  the  process  is  smooth  and  articular  and  enters  into  the 
formation  of  the  wrist  joint. 

Nutrient  foramina  are  numerous  around  the  neck.  The  main  one  for  the  shaft 
is  in  the  proximal  third  and  is  proximally  directed.  Small  foramina  are  also 
present  in  the  distal  extremity. 

Articulations. — With  the  humerus,  ulna  (both  ends)  and  the  navicular  and 
lunate  carpal  bones. 

Ossification. — It  is  of  endochondral  origin  and  is  developed  from  four  centers. 
Tlhil  for  the  shaft  appears  about  the  eighth  week;  that  for  the  distal,  extremity 
during  the  second  or  third  year  (eighth  to  the  fifteenth  month  (Pryor);  thai  for 
the  head  from  the  fifth  to  the  seventh  year;  that  for  the  tuberosity  during  the 
fourteenth  year.     By  the  twenty-third  year  all  are  fused  with  the  shaft. 


THE   CARPI'S  S 5 

Muscles  Attached. — Origins. — Mm.  flexor  digitorum  sublimis,  flexor  pollicis 
longus,  abductor  pollicis  longus,  extensor  pollicis  brevis. 

Insertions. — Mm.  biceps  brachii,  supinator,  pronator  teres,  pronator  quadratus 
and  brachioradialis  (nine). 

THE  BONES  OF  THE  HAND 

The  hand  comprises  the  wrist  (carpus,  eight  bones),  the  palm 
(metacarpus,  five  bones)  and  the  digits  (phalanges,  fourteen  bones). 

THE  CARPUS 

The  carpal  bones  are  arranged  in  two  rows  of  which  the  first,  or 
proximal  row  contains  the  navicular  (scaphoid),  os  I  una  turn  (semi- 
lunar), os  triquctrum  [cuneiform)  and  the  os  pisiforme.  The 
second,  or  distal  row  contains  the  greater  multangular  (trapezium), 
the  lesser  multangular  (trapezoid),  the  os  capitatum  (os  magnum)  and 
the  os  hamatum  (unciform)  bones.  These  are  given  from  radial  to 
ulnar  side.  They  are  all  irregular  bones.  The  dorsal  surfaces 
form  an  irregular  convex  surface  and  are  rough  for  the  attachment 
of  ligaments.  The  ventral  surfaces  are  irregular  and  together  form 
a  concave  or  groove-like  area  which  is  bridged  by  the  transverse 
carpal  ligament  and  constitutes  thus  a  canal  for  the  flexor  tendons 
of  the  fingers.  The  oilier  surfaces  are  articular  except  for  those  bones 
that  form  the  ends  of  the  rows  and  here  the  exposed  surface  of  each 
is  nonarticular.  The  navicular  and  os  lunatum  articulate  with  the 
distal  extremity  of  the  radius  and  the  distal  row  articulates  distally 
with  the  metacarpal  bones. 

These  bones  are  of  endochondral  origin  and  are  usually  carti- 
laginous at  birth.  According  to  J.  N.  Pryor  the  centers  appear 
earlier  than  formerly  supposed.  They  appear  earlier  in  the  female 
than  in  the  male.  Each  has  one  center  of  ossification  that  appears 
as  follows: 

Usually  given  Pryor 

Capitatum  appears  about  12th  mo.  (1).  3d  to  10th  mo. 


Os  hamatum 

Os  triquetrum 

Os  lunatum 

Greater  multangular 

Navicular 

Lesser  multangular 

Os  pisiforme 


14th  mo.  (2).  5th  to  the  i2mo. 

3d  year  (3).  2nd  to  3d  year 

5th  to  6th  year  (4).  3d  to  4th  year 

6th  year  (7).  4th  to  6th  year 

6th  year  (5).  4th  to  5th  year 

6th  to  7th  year  (6).  4th  to  6th  year 
nth  to  12th  year  (8).  9th  to  13th  year 


Ossification  is  completed  about  the  15th  year. 

Muscles  Attached. — 

Navicular. — M.  Abductor  pollicis  brevis  (origin). 

Os  Pisiforme. — Abductor  quinti  digiti  (origin),  flexor  carpi  ulnaris  (insertion). 
Great  Multangular. — Abductor  pollicis  brevis,  opponens  pollicis,  flexor  pollicis 
brevis  (deep  head) (all  origins). 

Lesser  Multangular. — Deep  head  of  flexor  pollicis  brevis   (origin) 


86 


OSTEOLOGY 


THE  PHALANGES  87 

Os  Capitation. — Deep  head  of  flexor  pollicis  brevis,  adductor  pollicis  (origins). 
Os  Hamatum  —  Opponens  quinti  digiti,  flexor  quinti  digiti  brevis  (origins), 
flexor  carpi  ulnaris  (insertion). 

THE  METACARPAL  BONES  (OSSA  METACARPALIA) 

The  metacarpal  bones  are  five  in  number  and  articulate  with  the 
distal  carpal  bones  and  each  other,  proximally,  and  with  the  first 
row  of  phalanges,  distally.  The  first,  or  thumb  metacarpal,  is  the 
most  mobile.     Each  consists  of  a  base,  shaft  and  head. 

The  base  is  the  carpal  extremity,  each  is  wedge-shaped  and  the 
articular  surface  varies  with  the  joint  that  it  forms.  The  first 
{thumb)  is  the  shortest  and  strongest.  The  second  (index  finger) 
is  the  longest.  The  shaft  of  each  is  smooth  and  narrow  in  the  middle. 
The  dorsal  surface  is  triangular  and  broad  distally.  The  ventral 
surface  is  narrow  and  more  like  a  ridge.  The  medial  and  lateral 
surfaces  are  concave  and  afford  origin  for  the  mm.  interossei.  The 
head  (capituium)  has  an  articular  surface  for  the  base  of  the  proximal 
phalanx.  This  surface  is  rounded  and  more  extensive  ventrallv 
than  dorsally.  The  ventral  edge  is  grooved  for  the  passage  of 
tendons.     To  the  margins  of  the  head  ligaments  are  attached. 

Nutrient  Foramina. — There  is  one  for  each  bone.  In  the  first  it  is  directed 
distally  while  in  the  others  it  is  proximally  directed. 

Ossification. — Each  of  the  four  medial  metacarpal  bones  has  one  center  for 
the  shaft  and  base  and  one  for  the  head.  The  shaft  and  base  center  appears 
(successively  and  in  order)  during  the  ninth  or  tenth  week  of  fetal  life;  the 
center  for  each  head  appears  during  the  third  year  and  fuses  completely  with 
the  shaft  by  the  twentieth  year.  The  center  for  the  shaft  and  head  of  the  first 
metacarpal  bone  appears  after  the  tenth  week  and  for  the  base  during  the  third 
year.      Fusion  with  the  shaft  takes  place  about  the  twentieth  year. 

Muscle  Attached. — First  Metacarpal. — Jim.  First  dorsal  interosseous  (origin). 
flexor  pollicis  brevis,  opponens  pollicis,  abductor  pollicis  longus  (insertions) 
(four). 

Second  Metacarpal. — First  and  second  dorsal  interossei,  first  palmar  interos- 
seous, adductor  pollicis  (origins);  flexor  carpi  radialis,  extensor  carpi  radialis 
longus  (insertions)  (six). 

Third  Metacarpal. — Second  and  third  dorsal  interossei,  adductor  pollicis 
transversus  and  obliquus  (origins);  extensor  carpi  radialis  brevis,  flexor  carpi 
radialis  (insertions)  (six). 

Fourth  Metacarpal. — Third  and  fourth  dorsal  interossei  and  second  palmar 
interosseous  (origins)  (three). 

Fifth  Metacarpal. — Extensor  carpi  ulnaris,  flexor  carpi  ulnaris,  opponens 
quinti  digiti  (insertions)  (three). 

THE  PHALANGES  (PHALANGES  DIGITORUM  MANTJS) 

The  phalanges  are  fourteen  in  number,  three  for  each  finger  and 
two  for  the  thumb.  The  first,  or  proximal  phalanges,  are  the 
longest  and  the  distal  are  the  smallest.  The  proximal  end  of  each 
first  phalanx  is  rather  large  and  bears  a  concave  articular  facet  for 
the  head  of  the  metacarpal  bone.     The  shaft  is  somewhat  flattened 


OSTEOLOGY 


THE    PELVIC    APPENDAGES  89 

and  presents  a  smooth  convex  dorsal  surface;  the  ventral  surface  is 
smooth  and  concave  for  the  accommodation  of  the  flexor  tendons. 
The  head  bears  a  convex  articular  facet  for  the  second  phalanx. 
The  second  phalanges  resembles  the  first  generally.  The  proximal 
facet,  however,  is  convex.  The  third  phalanges  are  the  smallest  and 
shortest.  The  proximal  extremity  is  large  and  its  articular  surface 
is  convex.  Its  distal  extremity  is  flattened  for  the  support  of  the 
nail. 

Nutrient  Foramina. — There  are  usually  two  nutrient  foramina  for  each  phalanx, 
distally  directed  and  upon  the  ventral,  or  palmar  surface. 

Ossification. — These  are  of  endochondral  origin  and  each  is  developed  from 
two  11  titers.  The  center  for  the  shaft  and  distal  extremity  appears  during  the  ninth 
to  the  tenth  week  of  fetal  life  and  that  for  the  proximal  extremity  during  the  third 
year.  According  to  Prvor  most  of  these  centers  appear  between  the  first  and 
early  part  of  the  third  years.  Fusion  of  these  parts  occurs  at  the  eighteenth  or 
twentieth  year. 

Muscles  Attached. — These  are  all  insertions. 
Thumb. — 

Fir>l  Phalanx. — Mm.  Extensor  pollicis  brevis,  flexor  pollicis  brevis,  adductor 
pollicis,  abductor  pollicis  brevis,  adductores  pollicis  obliquus 
and  transversus  (five). 
Set  ond  Phalanx. — Mm.  Flexor  pollicis  longus,  extensor  pollicis  longus  (two). 
Index  Finger. — 

First  Phalanx. — First  dorsal  and  first  palmar  interossei  (two). 
Second  Phalanx. — Mm.  Flexor  digitorum  sublimis,  extensor  digitorum  com- 
munis, extensor  indicis  (three). 
Third   Phalanx. — Mm.    Flexor   digitorum   profundus,    extensor    digitorum 
communis  (two). 
Middle  Finger. — 

First  Phalanx. — Second  and  third  dorsal  interossei  (two). 

Second   Phalanx. — Mm.    Flexor    digitorum    sublimis,    extensor    digitorum 

communis  (two). 
Third   Phalanx. — Mm.    Flexor   digitorum   profundus,    extensor    digitorum 
communis  (two). 
Ring  Finger. — 

First  Phalanx. — Fourth  dorsal  and  second  palmar  interossei  (two). 
Second  Phalanx. — Mm.  Flexor  digitorum  sublimis,  extensor  digitorum  com- 
munis (two). 
Third    Phalanx. — Mm.    Flexor    digitorum    profundus,    extensor    digitorum 
communis  (two). 
Little  Finger. — 

First  Phalanx. — Third  palmar  interosseus,  flexor  quinti  digiti  brevis,  abductor 

quinti  digiti  (three). 
Second    Phalanx. — Mm.    Flexor    digitorum    sublimis,    extensor    digitorum 

communis  (two). 
Third  Phalanx. — Mm.    Flexor   digitorum   profundus,    extensor    digitorum 
communis,  extensor  digiti  quinti  (three). 

THE  LOWER  LIMB  (PELVIC  APPENDAGES) 
The  pelvic  appendages  comprises  the  pelvic  girdle  and  the  append- 
ages proper.     The  girdle  is  formed  by  the  two  innominate  bones,  articu- 
lating with  each  other  ventrally  and  with  the  sacrum  dorsally. 


90  OSTEOLOGY 

THE  HIP  BONE  (OS  COXjE) 

The  hip  bone  is  classed  as  a  flat  bone;  it  is  shaped  like  a  propeller, 
one  blade  of  which  is  perforated  by  a  foramen  (obturator).  It 
represents  the  fusion  of  three  segments,  the  ilium,  ischium  and  os 
pubis.     These  surround  and  form  the  acetabular  cavity. 

The  ilium  is  the  largest  division  and  presents  two  surfaces,  three 
margins  and  four  spines.  The  lateral  surface  is  divided  into  a 
larger  (gluteal)  and  a  smaller  (acetabular)  portion.  The  gluteal 
portion  is  large,  concavoconvex  and  is  marked  by  the  three  gluteal 
lines.  The  inferior  gluteal  line  (linea  glutece  inferior)  lies  just  over 
the  acetabular  margin  and  between  these  two  the  reflected  head 
of  the  m.  rectus  femoris  arises.  The  ventral  {anterior)  line  is  the 
largest  and  starts  near  the  ventral  end  of  the  iliac  crest  and  arches 
dorsally  to  the  greater  sciatic  notch.  The  dorsal  {posterior)  gluteal 
line  is  a  short  curved  line  near  the  dorsal  portion  of  the  lateral  sur- 
face; dorsal  to  this  line  the  m.  gluteus  maximus  arises.  The  m. 
gluteus  medius  arises  between  the  ventral  and  dorsal  lines  and  the 
iliac  crest.  The  medial  surface  is  divided  into  dorsal  and  ventral  por- 
tions. The  dorsal  part  is  partly  articular  (fades  articular  is)  for  articu- 
lation with  the  sacrum.  Superiorly  and  dorsally  the  bone  is  rough- 
ened and  presents  a  tuberosity  {tuberositas  iliaca)  and  serves  for  the 
attachment  of  ligaments.  The  superior  edge  here  gives  origin  to 
the  mm.  multifidus,  sacrospinalis  and  quadratus  lumborum.  The 
ventral  portion  is  mainly  concave,  smooth  and  presents  the  extensive 
iliac  fossa  from  which  the  m.  iliacus  arises.  The  oblique  iliopectineal 
line  {linea  arcuala),  which  bounds  the  fossa  inferiorly,  ends  ventrally 
in  the  iliopectineal  eminence.  The  dorsosuperior  portion  of  this 
surface  gives  origin  to  the  m.  obturator  internus. 

The  iliac  crest  {crista  iliaca)  has  a  lateral  lip  (labrum  lateralis), 
a  medial  lip  (labrum  medialis)  and  an  intervening  area  (linea  inter- 
media). The  crest  is  in  the  form  of  a  quarter  circle  and  extends 
from  the  ventral  superior  spine  to  the  dorsal  superior  spine  in  a 
double  curve.  From  the  dorsal  part  of  the  crest  the  mm.  quadratus 
lumborum,  latissimus  dorsi  and  sacrospinalis  arise;  on  the  ventral 
part  the  mm.  obliquus  abdominis  internus  and  transversus  ab- 
dominis arise  and  the  oblique  abdominis  externus  is  inserted.  The 
ventral  superior  spine  (spina  ilia-ca  anterior  superior)  is  a  blunt  process 
that  affords  origin  to  the  m.  sartorius  and  laterally  to  the  m.  tensor 
fascia?  lata?  and  the  inguinal  ligament.  The  ventral  inferior  spine 
(spina  iliaca  anterior  inferior)  is  below  the  preceding  and  gives 
origin  to  the  m.  rectus  femoris  and  the  iliofemoral  ligament.  The 
ventral  margin  connects  the  two  ventral  spines.  The  dorsal  superior 
spine  is  at  the  termination  of  the  iliac  crest.  From  it  the  dorsal 
margin  starts  and  a  short  distance  below  its  origin  it  presents  the 


THE    HIP    BONE 


91 


92  OSTEOLOGY 

dorsal  inferior  spine;  below  this  the  margin  is  deeply  notched;  this 
constitutes  the  greater  sciatic  notch  (incisura  ischiadica  major). 

The  ischium,  the  dorsoinferior  portion  of  the  os  coxae,  presents 
a  body  and  two  rami.  The  body  {corpus)  is  the  superior  part  of  the 
bone.  Its  lateral  surface  is  irregular,  presenting  a  deep  acetabular 
notch  that  forms  two-fifths  of  the  acetabular  cavity.  The  bone 
beyond  this  slopes  from  the  margin  of  the  cavity  and  is  smooth. 
The  medial  surface  is  smooth,  concave  and  forms  a  part  of  the  wall 
of  the  pelvic  cavity.  The  short  ventral  margin  assists  in  forming  the 
obturator  foramen.  The  medial  margin  presents  the  ischial  spine 
(spina  ischiadica);  this  bounds  the  lesser  sciatic  notch  superiorly 
and  affords  origin  to  the  m.  gemellus  superior  and  the  sacrospinous 
ligament;  laterally  it  gives  origin  to  the  m.  coccygeus  and  medially 
to  the  m.  levator  ani.  The  rami  are  two  wedge-shaped  bars  of  bone 
that  join  each  other  at  nearly  a  right  angle.  The  ventral  surface  of 
each  is  concave  and  the  inferior  affords  origin  to  the  mm.  obturator 
externus,  and  adductor  magnus.  The  medial  surfaces  are  flat  and 
afford  an  origin  to  the  crus  penis  (or  clitoridis)  and  mm.  ischiocavern- 
osus,  obturator  internus  and  transversus  perinei.  The  medial 
margin  of  each  ramus  is  thin  and  assists  in  forming  the  boundary  of 
the  obturator  foramen.  The  dorsolateral  margin  of  the  superior 
ramus  presents  a  rough  irregular  mass  of  bone,  the  tuberosity  (tuber 
ischiadicum);  from  this  arise  the  mm.  semitendinosus  (superiorly 
and  laterally)  and  the  biceps  femoris  and  semimembranosus 
(inferiorly  and  medially). 

The  pubis  (os  pubis)  is  the  smallest  division  and  is  ventrally 
placed.     It  comprises  a  body  and  two  rami. 

The  body  (corpus)  presents  two  surfaces.  The  dorsoinferior  surface 
is  smooth  and  affords  origin  to  the  m.  levator  ani  and  the  pubo- 
prostatic ligament.  The  ventroiuferior  surface  is  rough  and  affords 
origin  to  the  mm.  gracilis,  adductores  longus  et  brevis  and  the 
obturator  externus.  The  medial  margin  (fades  symphyseos)  is  oval, 
covered  with  cartilage  and  joins  its  fellow  of  the  opposite  side  to  form 
the  symphysis  pubis.  The  superior  margin  is  thick  and  extends  so 
as  to  form  the  crest  and  tubercle.  The  crest  gives  origin  to  the  mm. 
rectus  abdominus  and  pyramidalis  and  the  tubercle  affords  attach- 
ment to  the  inguinal  ligament.  The  superior  ramus  slopes  superiorly 
and  laterallv  and  its  lateral  extremity  forms  a  part  of  the  acetabular 
cavity.  Its  ventrosuperior  surface  affords  origin  to  the  m.  pectineus. 
The  dorsosuperior  (medial)  surface  is  concave  and  forms  a  part  of  the 
pelvic  wall.  The  ventroiuferior  surface  is  concave.  The  inferior 
margin  (crista  obturatoria)  forms  a  part  of  the  boundary  of  the  obtu- 
rator foramen.  The  dorsosuperior  margin  is  a  continuation  of  the 
iliopectineal  line  and  is  called  the  pecten  ossis  pubis.  The  interior 
ramus  is  flattened  and  has  a  downward  and  lateral  direction;  it 


THE    PELVIS  93 

completes  the  boundary  of  the  obturator  foramen  and  with  its  fellow- 
forms  the  pubic  arch.  Its  ventral  surface  gives  origin  to  the  mm. 
gracilis  and  adductores  magnus  et  brevis.  Its  smooth  medial  sur- 
ace  and  inferior  margin  give  attachment  to  the  crus  penis  or  clito- 
ritis  and  the  arcuate  ligament. 

The  obturator  foramen  (foramen  obturation)  is  the  opening  between 
the  above  bones.  This  is  closed  in  by  a  membrane  in  the  fresh 
condition. 

The  acetabulum  is  a  deep  cavity  formed  by  the  above  bones;  the 
ilium  forms  a  little  less  than  two-fifths,  the  ischium  a  little  more  than 
two-fifths  and  the  pubis  one-fifth.  Opposite  the  obturator  foramen 
the  margin,  to  which  the  capsular  ligament  is  attached,  is  interrupted 
and  this  is  the  acetabular  notch  (incisura  acetabuli).  The  articular 
portion  of  the  floor  is  horseshoe-shaped  and  the  central  depressed 
area  (fossa  acetabuli)  is  continuous  with  the  acetabular  notch. 

Nutrient  foramina  are  numerous;  for  the  ilium  in  the  iliac  fossa  and  pelvic  and 
gluteal  areas;  for  the  ischium  near  the  acetabulum  and  upon  the  pelvic  portion; 
for  the  pubis  in  the  acetabular  fossa  and  in  the  body. 

Articulations. — With  the  femur,  sacrum  and  fellow  of  the  opposite  side. 

Ossification. — It  is  of  endochondral  origin.  The  primary  centers  appear  early; 
the  center  for  the  ilium  about  the  ninth  week  of  fetal  life;  for  the  ischium  about 
the  fourth  month;  for  the  pubis  about  the  fifth  to  the  sixth  month  of  fetal  life. 
Up  to  the  twelfth  year  these  bones  are  still  separated  from  one  another  by  car- 
tilage in  the  acetabular  cavity;  at  that  time  about  three  centers  appear  here  and 
fusion  is  completed  by  the  sixteenth  year.  At  about  the  age  of  puberty  other 
centers  appear;  one  for  the  ventroinferior  spine,  twelfth  year;  one  for  the  ventral 
two-thirds  of  the  iliac  era!  and  superior  spine,  fifteenth  year;  one  for  the  dorsal 
one-third  of  the  iliac  crest  and  the  dorsal  superior  spine,  fifteenth  year;  one  for  the 
tuberosity  of  the  ischium,  fifteenth  year:  one  or  two  for  the  tubercle  and  angle  of 
the  pubis.     These  all  fuse  with  the  body  by  the  twenty-fifth  year. 

Muscle  Attached. —  Origins. — Mm.  tensor  fascia?  lata?,  latissimus  dorsi,  trans- 
versa abdominis,  quadratus  lumborum,  sacrospinalis,  obliquus  abdominis 
internus,  gluteus  maximus,  gluteus  medius,  gluteus  minimus,  rectus  femoris, 
iliacus,  pyriformis,  rectus  abdominis,  pyramidalis,  obturator  internus,  obturator 
externus,  ischiocavernosus.  transversus  perinei,  gemelli  superior  and  inferior, 
levator  ani,  coccygeus,  biceps  femoris,  semitendinosus,  semimembranosus, 
adductores  magnus  and  brevis,  pectineus,  gracilis  and  adductor  longus. 

Insertion. — M.  obliquus  abdominis  externus. 

THE  PELVIS 

The  pelvis  consists  of  the  two  ossa  coxa-,  sacrum  and  coccyx.  That 
portion  superior  to  the  iliopectineal  lines  constitutes  the  false  pelvis 
(pelvis  major)  and  that  below  the  true  pelvis  (pelvis  minor).  The 
pelvis  minor  is  bounded,  ventral! y,  by  the  symphysis  pubis,  the  bodies 
and  superior  rami  of  the  pubic  bones;  laterally  by  the  body  of  the 
ischium  and  its  rami  and  dorsally  by  the  sacrum  and  coccyx.  The 
superior  aperture,  or  brim,  slopes  downward  and  forward  at  an 
angle  of  6o°  to  the  horizontal  plane;  it  is  bounded,  ventral! y,  by  the 


94  OSTEOLOGY 

bodies  of  the  ossa  pubes,  laterally  by  the  iliopectineal  lines  and 
dorsally  by  the  promontory  of  the  sacrum.  The  inferior  aperture, 
or  outlet,  is  bounded,  venlrally  and  superiorly,  by  the  bodies  of  the 
ossa  pubes,  laterally  by  the  rami  of  pubes  and  ischii  and  ischial 
tuberosity  and  dorsally  by  the  tip  of  the  coccyx  and  sacrotuberous 
ligaments.  The  ventral  wall  is  only  i>2  to  2  inches  vertically  and 
the  dorsal  wall  5  to  6  inches  in  extent. 

The  female  pelvis  is  lighter  and  smoother  and  the  iliac  bones  do 
not  flare  out  as  much  as  in  the  male.  The  cavity  is  more  capacious, 
the  sacrum  shorter  and  wider,  the  sacral  curve  less  uniform  and  the 
pelvic  arch  is  wider  in  the  female.  The  superior  aperture  is  large 
and  more  oval;  the  outlet  is  larger  and  the  ischial  tuberosities  are 
farther  apart  in  the  female. 

THE  FEMUR 

The  femur  is  the  longest  bone  in  the  body  and  comprises  a  proxi- 
mal extremity,  shaft  and  a  distal  extremity. 

The  proximal  extremity  consists  of  head,  neck  and  two  trochanters. 
The  head  (caput  femoris)  is  the  articular  portion.  It  is  hemispherical 
in  shape,  fits  into  the  acetabular  cavity  and  near  its  summit  exhibits 
a  depression  (fovea  capitas  femoris)  in  which  the  ligamentum  teres 
is  attached.  The  neck  (folium  femoris)  is  shaped  like  an  old-fash- 
ioned mortar,  supports  the  head  and  is  attached  by  its  base  to  the 
shaft,  at  an  angle  of  1250.  Ventrally  and  dorsally  its  junction  with 
the  shaft  is  marked  by  oblique  ridges;  the  ventral  ridge  is  the  superior 
portion  of  the  intertrochanteric  line  and  to  it  is  attached  the  ilio- 
femoral ligament.  The  dorsal  ridge  connects  the  two  trochanters 
and  is  called  the  intertrochanteric  crest;  part  of  this,  the  quad  rat  or 
tubercle,  affords  insertion  to  the  m.  quadratus  femoris.  Vascular 
foramina  are  numerous  in  the  neck. 

The  greater  trochanter  (trochanter  major)  is  a  quadrilateral  mass  of 
bone  that  projects  from  the  shaft  above  the  level  of  the  neck.  Its 
medial  surface  is  quite  concave,  forming  the  trochanteric  fossa  where 
the  m.  obturator  externus  is  inserted.  The  lateral  surface  is  some- 
what convex  and  presents  an  oblique  ridge  into  which  the  m.  gluteus 
minimus  is  inserted.  To  its  proximal,  or  superior  margin  the  mm. 
obturator  internus  and  gemelli  are  inserted  (ventrally)  and  the 
pyriformis  (dorsally).  The  dorsal  margin  is  the  superior  portion  of 
the  intertrochanteric  crest. 

The  lesser  trochanter  (trochanter  minor)  is  a  blunt,  cone-shaped 
mass  of  bone  upon  the  dorsal  surface  at  the  junction  of  the  shaft  and 
neck  and  at  a  lower  level  than  the  greater  trochanter.  Here  the 
intertrochanteric  crest  ends.  To  this  trochanter  the  m.  iliopsoas  is 
inserted. 

The  shaft  is  cylindrical  and  curved  from  above  downward  with 


1HE  FEMUR 


95 


the  convexity  ventrally  directed.  It  becomes  broader  where  it 
supports  the  distal  extremity.  Margins  are  not  present  as  the  gen- 
eral curvature  of  the  circumference  causes  the  surfaces  to  blend 
insensible  with  one  another.     Upon  the  dorsal  surface  is  a  narrow 


Great  trochanter 


Oreat  trochanter 


Internal  epicondyle 


Internal 

condyle  i 

Intercondyloid  line 


\       External  condyle 
Intercondyloid  ft 


Fig.  66. — The  right  femur  seen  from 
behind.     (Soboila  and  AlcMurrich.) 


FlG.  67. — The  right  femur  see 
front.     (.Sobotta  and  McMu 


1  from  i 
rich.) 


rough  area  called  the  linca  aspera.  The  medial  edge,  or  lip,  of  the 
linea  aspera  continues,  superiorly,  around  the  base  of  the  trochanter 
minor  where  it  becomes  continuous  with  the  ventral  intertrochanteric 
line;  these  two  constitute  the  spiral  line  from  which  the  m.  vastus 
medialis  arises.  The  lateral  Up  of  the  linea  aspera  is  continued, 
superiorly,  to  the  level  of  the  trochanter  minor  as  the  gluteal  tuber- 


96  OSTEOLOGY 

osity.  This  is  rough  and  serves  for  the  insertion  of  the  m.  gluteus 
maximus.  The  pectineal  line  lies  between  these  two  and  serves  for 
the  insertion  of  the  m.  pectineus.  In  the  middle  of  the  shaft  the 
lips  of  the  linea  aspera  are  most  prominent.  The  mm.  adductores 
magnus,  longus  and  brevis  are  inserted  into  the  proximal  portion 
between  the  mm.  gluteus  maximus  and  pectineus.  In  the  distal 
third  the  lips  diverge  and  end  at  the  corresponding  epicondyles  as 
the  epicondylic  lines.  The  triangular  area  between  these  lines  is  the 
popliteal  plane  (planum  poplitcum)  which  is  part  of  the  floor  of  the 
popliteal  fossa.  The  adductor  tubercle  is  a  small  eminence  at  the  end 
of  the  medial  epicondylic  line;  to  its  medial  surface  the  tendon  of 
the  m.  adductor  magnus  is  inserted  and  from  its  dorsal  surface  the 
m.  gastrocnemius  (medial  head)  arises.  The  medial  lip  and  the 
adjoining  medial  surface  of  the  shaft  afford  origin  for  the  m.  vastus 
medialis;  the  lateral  lip  and  lateral  surface  afford  origin  for  the  m. 
vastus  lateralis;  the  ventral  surface  of  the  shaft  affords  origin  to  the 
mm.  vastus  intermedius  and  articularis  genu.  The  m.  biceps  fe- 
moris  arises  from  the  lateral  lip  distal  to  the  m.  gluteus  maximus 
and  also  from  the  lateral  epicondylic  line.  The  distal  portion  of  the 
same  line  gives  origin  (dorsally)  to  the  m.  plantaris. 

The  distal  extremity  consists  of  the  two  condyles  and  two  epicondyles. 
The  condyles  are  two  rocker-like  articular  processes  of  the  bone; 
the  articular  surface  of  the  two  condyles  are  connected  ventrally 
(patellar  area)  and  are  separated  dorsally  by  the  intcrcondylic  notch 
or  fossa.  When  the  bone  is  held  vertically  the  medial  condyle 
projects  farther  distally  but  is  narrower  and  less  extensive  dorso- 
ventrally  than  the  lateral  condyle.  The  intercondylic  notch  is  quite 
deep  and  broad.  To  the  medial  wall  is  attached  the  dorsal  cruciate 
ligament  and  on  its  lateral  wall  is  attached  the  ventral  cruciate 
ligament.  Where  the  floor  of  the  notch  joins  the  popliteal  plane 
there  is  a  ridge  to  which  the  dorsal  part  of  the  capsular  ligament 
is  attached.  The  medial  epicondyle  affords  attachment  to  the 
tibial  collateral  ligament  of  the  knee  joint.  The  lateral  epicondyle 
is  less  prominent  and  presents  a  dorsal  groove  {popliteal)  that  ends 
in  a  pit  ventrally.  Here  the  m.  popliteus  arises.  The  dorsal  por- 
tion of  the  epicondyle  affords  attachment  to  the  fibular  collateral 
ligament  of  the  knee  joint  and  to  the  lateral  head  of  the  m. 
gastrocnemius. 

The  articular  surface  consists  of  the  patellar  and  condylic  portions. 
The  patellar  part  (jacies  patellaris)  is  concave  in  the  middle  and  is 
separated  from  each  condylar  surface  by  an  oblique  groove.  The 
lateral  condylic  surfaces  are  convex  in  both  directions  and  are  on 
the  distal  and  dorsal  portions  of  the  condyle.  The  medial  is 
narrower  than  the  lateral. 


THE    PATELLA  QJ 

Nutrient  foramina  are  found  in  the  fossa  for  the  ligamentum  teres,  the  neck, 
on  the  great  trochanter,  on  the  linea  aspera  (proximally  directed)  and  in  the 
intercondylic  fossa. 

Articulations. — With  the  hip  bone,  tibia  and  patella. 

Ossification. — It  is  of  endochondral  origin  and  is  developed  from  five  centers. 
The  centers  for  the  shaft  appears  during  the  second  fetal  month;  that  for  the  distal 
extremity  during  the  ninth  month;  that  for  the  head  during  the  first  year;  the 
center  for  the  greater  trochanter  about  the  second  to  the  third  year;  that  for  the 
lesser  trochanter  about  the  twelfth  to  the  thirteenth  year.  All  fuse  with  the  shaft 
by  the  twentieth  to  the  twenty-second  year. 

Muscles  Attached. — Origins. — Mm.  vasti  medialis,  lateralis  and  intermedius. 
short  head  of  biceps  femoris,  gastrocnemius,  popliteus,  plantaris  and  articularis 
genu. 

Insertions. — Mm.  glutei  maximus,  medius  and  minimus,  gemelli  superior  and 
inferior,  pyriformis,  obtutatores  internus  and  externus,  psoas,  iliacus,  quadratus 
femoris,  adductores  magnus,  brevis.  and  longus,  and  pectineus  (twenty-three). 

THE  PATELLA 

The  patella  is  a  sessamoid  bone,  that  is  one  that  is  developed  in 
a  tendon.  It  protects  the  knee  joint  ventrally.  It  is  flattened,  of 
a  triangular  outline  (inverted)  and  possesses  an  apex,  a  base,  two 
surfaces  and  two  margins. 

The  apex  (apex  palel/ce)  is  distal  and  affords  attachment  to  the 
ligamentum  patellae.     The  base  (basis  patella)  is  broad  and  thick  and 

Base  Base 


Apex  Apex 

Fig.  68. — The  patella  seen  from  in  front.  Fig.  69. — The  patella  seen  from  behind. 

-■■•iia  ami  McMurrich.)  (Sobotta  and  McMurrich.) 

receives,  ventrally,  the  insertion  of  the  tendon  of  the  m.  quadriceps 
extensor.  The  ventral  surface  is  convex,  somewhat  rough,  subcu- 
taneous and  has  numerous  foramina.  The  dorsal  surface  is  mainly 
articular.  A  vertical  ridge  divides  it  into  a  larger,  concave  lateral 
facet,  for  the  lateral  condyle  of  the  femur,  and  a  smaller,  concave 
medial  facet  for  the  medial  condyle  of  the  femur.  The  nonarticular 
portion  is  the  dorsal  surface  of  the  apex  and  here  the  synovial  mem- 
brane of  the  knee  joint  is  attached.  The  medial  and  lateral  margins 
are  convex  and  afford  insertion  to  the  mm.  vasti  medialis  and 
lateralis,  respectively. 


90  OSTEOLOGY 

Nutrient  foramina  are  seen  upon  the  ventral  surface. 

Articulations. — With  the  femur. 

Ossification. — It  is  of  endochondral  origin  and  develops  from  one.  or  two 
centers,  which  appear  during  the  third  year.  Ossification  is  usually  com- 
pleted by  the  age  of  puberty. 

Muscles  Attached. — Insertions. — Mm.  vasti  medialis,  lateralis  and  intermedins 
and  the  rectus  femoris  (four). 

THE  TIBIA 

The  tibia  or  shin  bone  is  the  larger  and  stronger  bone  of  the  leg. 
It  consists  of  a  proximal  extremity,  shaft  and  distal  extremity. 

The  proximal  extremity  comprises  the  condyles,  the  intercondylic 
eminence  and  the  tuberosity.  The  condyles  constitute  a  flat  mass 
that  caps  the  proximal  end  of  the  shaft.  The  proximal  surface  of  each 
condyle  is  concave  and  articular.  The  lateral  is  the  smaller  and 
nearly  circular  in  outline.     Near  the  middle  of  the  intercondylic 

Anterior  intereondyloid  fossa 

^   Tuberosity  of  tibia 


cimal  extremities  of  the  right  tibia  ; 
(Sobot'a  and  McMurrich.) 

area  is  the  intercondylic  eminence  [cmincntia  intcrcondyloidea); 
this  presents  two  peaks,  or  tubercles,  the  tubcrculum  inter condyloideum 
lalerale  and  tub.  inter,  mediate.  The  depression  ventral  and  dorsal 
to  the  eminence  constitute  the  ventral  and  dorsal  intercondyloid 
fossce.  Here  are  attached  the  ventral  and  dorsal  cruciate  liga- 
ments and  the  menisci  of  the  knee  joint.  The  lateral  condyle 
projects  well  beyond  the  side  of  the  shaft  and  presents  a  small 
dorsolateral  facet  for  articulation  with  the  proximal  extremity  of 
the  fibula.  Ventrally  the  iliotib  al  band  (trackis  iliotibialis)  is 
attached,  the  tendon  of  the  m.  biceps  femoris  is  inserted  and  the 
mm.  extensor  digitorum  longus  and  peroneus  longus  arise.  The 
dorsomedial  margin  of  the  medial  condyle  is  grooved  for  the  inser- 
tion of  the  m.  semimembranosus.  The  tuberosity  is  slightly  distal 
to  the  condyles;  its  proximal  portion  is  covered  by  a  bursa  while 
the  distal  part  receives  the  insertion  of  the  ligamentum  patella?. 

The  shaft  (corpus  tibia')  presents  three  surfaces  and  three  margins. 
Its  proximal  three-fourths  is  wedge-shaped  (triangular  in  section) 


THE    TIBIA 


99 


and  its  distal  one-fourth  is  somewhat  flattened.  The  medial  surface, 
flat  or  convex,  is  extensive  but  mainly  subcutaneous.  On  its 
proximal  portion  the  mm.  gracilis  and  semitendinosus  are  inserted. 


Fig.  71. — The  right  tibia  seen  from 
front.      (Sobolta  and  McMumch.) 


Inferior  extremity 


Fig.   7^- — The  right  tibia,  seen  from 
behind.  (Sobotta  and  McMurrich.) 


The  proximal  portion  of  the  lateral  surface  is  quite  extensive  and 
affords  an  extensive  origin  to  the  m.  tibialis  anterior;  distally  it 
turns  and  blends  with  the  medial  surface  a  sort  of  ventral  surface. 
This  is  covered  by  the  tendons  of  the  mm.  tibialis  anterior,  extensor 
hallucis  proprius  and  the  ext.  digitorum   communis.     The  dorsal 


IOO  OSTEOLOGY 

surface  is  extensive  and  is  usually  convex  proximally  and  flat  distally. 
The  convex  portion  is  crossed  by  the  oblique  popliteal  line  proximal 
to  which  the  m.  popliteus  is  inserted;  from  the  oblique  line  the  m. 
soleus  arises.  From  the  bulk  of  the  remainder  of  the  surface  the 
mm.  tibialis  posterior  (laterally)  and  the  flexor  digitorum  longus 
(medially)  arise.  The  distal  portion  is  merely  covered  by  these 
tendons  and  the  tendon  of  the  m.  flexor  hallucis  proprius.  A  nutrient 
canal  (distally  directed)  is  present  on  this  surface.  The  ventral 
margin,  or  crest  is  prominent  in  the  proximal  three-fourths  and  subcu- 
taneous. The  medial  margin  is  prominent  in  its  middle  third  only. 
The  lateral  margin,  or  interosseous  crest  (crista  inter ossea)  is  sharp 
and  to  it  the  interosseous  membrane  is  attached.  Distally  it  is 
divided  into  two  lines  that  diverge  and  enclose  the  articular  surface 
for  the  distal  extremity  of  the  fibula  and  the  area  for  the  attachment 
of  the  ligaments  of  this  joint. 

The  distal  extremity  is  quite  large  and  exhibits  an  articular  surface 
and  a  malleolus.  The  articular  surface  is  on  the  inferior,  or  distal 
portion;  this  is  triangular  and  saddle-shaped  and  rests  upon  the 
articular  surface  of  the  astragalus  (talus).  Upon  the  lateral  margin 
of  the  extremity  (base  of  the  triangle)  there  is  a  notch  (incisura 
fibularis)  for  articulation  with  the  fibula  and  the  articular  cartilage 
lines  the  notch.  The  medial  angle  of  this  extremity  projects  in- 
feriorly  as  the  medial  malleolus.  The  medial  aspect  of  the  malleolus 
is  subcutaneous  and  its  lateral  aspect  is  articular  forming  a  part  of 
the  ankle  joint.  It  also  serves  for  the  attachment  of  the  tibial 
collateral  ligament.  Its  dorsal  surface  has  two  grooves,  one  for 
the  tendons  of  the  mm.  tibialis  posterior  and  the  flexor  digitorum 
longus  and  the  other  for  the  tendon  of  the  m.  flexor  hallucis  longus. 

Nutrient  foramina  are  numerous  in  the  condylar  portion,  the  intercondyloid 
fossae  and  the  eminence;  the  main  one  for  the  shaft  is  on  the  dorsal  surface  and 
is  distally  directed.  The  margins  of  the  distal  extremity  also  shows  numerous 
foramina. 

Articulations. — With  the  femur,  fibula  and  astragalus. 

Ossification. — This  is  of  endochondral  origin  and  develops  from  three  or  four 
centers.  The  center  for  the  shaft  appears  during  the  second  fetal  month.  The 
renter  for  the  proximal  extremity  appears  before  birth  and  for  the  distal  extremity 
between  the  first  and  second  years.  The  center  for  the  tuberosity,  when  independ- 
ent, appears  at  about  the  eleventh  year.  Complete  fusion  with  the  shaft  takes 
place  by  the  twentieth  to  the  twenty-fourth  year. 

Muscle  Attached. — Origins. — Mm.  tibialis  anterior,  extensor  digitorum  longus, 
soleus,  flexor  digitorum  longus,  tibialis  posterior,  peroneus  longus. 

Insertions. — Mm.  biceps  femoris,  semimembranosus,  semitendinosus,  sartorius, 
gracilis,  popliteus,  quadriceps  extensor  (thirteen). 

THE  FIBULA 

The  fibula  is  the  slender  bone  on  the  lateral  side  of  the  leg  but  it 
does  not  support  the  body.  It  consists  of  two  extremities  and  a 
shaft. 


THE    FIBULA 


The  proximal  extremity  or  head  (capitulum  fibula)  is  broad,  flat, 
and  pointed.  This  point  is  the  apex  to  which  the  fibular  collateral 
ligament  is  attached  and  the  m.  biceps  femoris  is  inserted.  The 
medial  surface  slopes  medially  and  distally  and  has  an  articular 
facet  that  fits  against  the  articular  facet  upon  the  lateral  condyle 
of   the   tibia.     The  lateral  surface  is   somewhat   roughened.     The 


-    Anterior  crest 


Inferior  extremity  —> 

Peroneal 


Fic.   73. — The  right  fibula,  seen  from 
the  medial  surface.     (Sobolta  and  Mc- 


FlG.  74. — The  right  fibula,  seen  from 
he  lateral  surface.      (Sobotla  and  Mc- 


tendon  of  the  m.  biceps  femoris  is  inserted  to  the  ventral  and 
proximal  surface  and  below  this  the  m.  peroneus  longus  arises;  its 
dorsal  part  gives  origin  to  the  m.  soleus.  The  next  portion  of  the 
bone  is  somewhat  constricted  and  is  called  the  neck. 

The  shaft  (corpus  fibula)  is  exceedingly  variable  as  to  shape  and 
form.  It  has  three  surfaces,  three  margins  and  an  interosseous  crest. 
The  medial  surface  is  divided  into  ventral  and  dorsal  areas  by  the 
interosseous  crest  to  which  the  interosseous  membrane  is  attached. 
The  ventral  part  of  this  surface  is  variable  in  width  and  affords  origin 
to  the  mm.  extensor  digitorum  communis,  extensor  hallucis  longus 
and  peroneus  tertius.     The  dorsal  part  of  this  surface  is  less  exten- 


OSTEOLOGY 


sive,  lies  dorsal  to  the  interosseous  crest  and  affords  origin  to  the 
m.  tibialis  posterior.  The  lateral,  or  peroneal  surface,  in  its  proximal 
part,  faces  ventrally  and  in  its  distal  part  faces  dorsally.  It  gives 
origin  to  the  mm.  peronei  longus  and  brevis.  The  dorsal  surface  is 
fairly  extensive  but  irregular.  Proximally  the  m.  soleus  arises  while 
distally  the  m.  flexor  hallucis  longus  arises. 

The  ventral  margin,  or  crest,  separates  the 
medial  and  lateral  surfaces  and  to  it  the  in- 
termuscular fascia  that  separates  the  peroneal 
from  the  ventral  muscles  is  attached.  The 
lateral  margin,  or  crest  is  fairly  well  marked 
(distally)  and  separates  the  lateral  and  dorsal 
surfaces.  From  its  proximal  end  the  m. 
soleus  arises.  The  medial  margin,  or  crest,  is 
a  curved  ridge  dorsal  to  the  interosseous  crest 
and  serves  to  separate  the  smaller  dorsal  part 
of  the  medial  surface  (from  which  the  m. 
tibialis  posterior  arises)  from  the  larger  dorsal 
surface  of  the  shaft.  The  crest  gives  at- 
tachment to  the  deep  fascia  that  covers  the 
m.  tibialis  posterior. 

The  distal  extremity  is  called  the  lateral 
malleolus  (malleolus  lateralis).  It  is  an  ir- 
regular mass  of  bone  with  a  blunt  point. 
The  lateral  surface  is  convex  and  mainly 
subcutaneous.  The  medial  surface  exhibits 
a  facet  for  articulation  with  the  astragalus 
(talus).  Dorsal  to  this  is  a  pit  for  the  at- 
tachment of  the  astragulofibular  ligament, 
and  proximally  the  roughened  surface  gives 
attachment  to  the  interosseous  ligaments. 
The  dorsal  surface  shows  a  groove  (sulcus 
malleolaris)  for  the  passage  of  the  tendons  of 
the  mm.  peronei  longus  and  brevis.  The 
ventral  margin  gives  attachment  to  the  astrag- 
alofibular  and  calcaneofibular  ligaments. 

Arterial  Foramina. — These  are  numerous,  some  in  the  head  and  some  in  the 
malleolus.    The  largest  is  on  the  dorsal  surface  of  the  shaft  and  is  distally  directed . 

Articulations. — With  the  tibia  (proximally  and  distally)  and  with  the  as- 
tragalus (talus). 

Ossification. — It  is  of  endochondral  origin  and  arises  from  three  centers. 
The  center  for  the  shaft  appears  during  the  middle  of  the  second  month  of  fetal 
life.  The  center  for  the  distal  extremity  appears  during  the  second  year  and  for 
the  proximal  extremity  during  the  third  or  fourth  year.  Fusion  with  the  shaft 
is  completed  between  the  twentieth  and  twenty-fourth  years. 

Muscles  Attached. — Origins. — Mm.  soleus,  peronei  longus,  brevis  and  tertius, 


Fie.  75.— The  tibia  and 
fibula  seen  from  behind. 
(Sobotta  and  McMurrich.) 


THE    TARSUS  IOJ 

tibialis  anterior  and    posterior,  flexor  hallucis  longus.  extensor  digitorum  com- 
munis and  extensor  hallucis  longus. 
Insertions. — M.  biceps  femoris. 

THE  BONES  OF  THE  FOOT 

The  foot  comprises  the  tarsus,  metatarsus  and  the  phalanges. 
THE  TARSUS 

The  tarsal  bones  (ossa  tarsi)  are  the  astragalus,  calcaneum,  scaphoid, 
three  cuneiform  and  cuboid  bones.     All  are  irregular  in  shape. 

The  astragalus  (talus)  forms  the  tarsal  part  of  the  ankle  and 
supports  the  tibia.     It  consists  of  a  body,  head  and  neck. 

The  body  presents  a  superior,  saddle-shaped  facet  for  articulation 
with  the  tibia.  The  articular  surface  extends  laterally  for  articula- 
tion with  the  malleolus  of  the  fibula  and  medially  for  articulation 
with  the  malleolus  of  the  tibia.  Around  these  areas  ligaments  of  the 
joint  are  attached.  The  distal  surface  presents  two  articular  facets; 
the  dorsal  one  (dorsal  calcaneal  facet)  is  concave  for  articulation 
with  the  dorsal  facet  upon  the  calcaneus.  The  ventral  facet  (middle 
calcaneal  facet)  is  slightly  convex  for  articulation  with  the  facet  upon 
the  sustentaculum  tali  of  the  calcaneum.  Between  the  two  there  is 
a  deep  groove  {sulcus  tali).  The  oval  head  presents  a  convex  articular 
facet  on  its  ventral  surface;  this  articulates  with  the  scaphoid 
(navicular)  bone.  Ventral  and  lateral  to  the  middle  calcaneal  facet 
is  the  ventral  calcaneal  facet.  Upon  the  infer omedial  surface  of  the 
head  is  another  facet  that  rests  upon  the  plantar  calcaneonavicular 
ligament.  The  neck  is  a  groove  and  is  best  marked  dorsally  where  it 
separates  the  body  and  head. 

Articulations. — With  the  tibia,  fibula,  calcaneum  and  scaphoid  (navicular). 
Muscles  Attached. — Xone. 

The  calcaneum,  or  heel  bone,  is  the  largest  of  the  tarsal  bones.  It 
is  an  irregular  mass  the  dorsal  portion  of  which  projects  as  the  heel 
and  is  called  the  tuberosity  (tuber  calcanei).  To  the  middie  of  its 
dorsal  surface  the  tendo  Achillis  (calcaneus)  is  attached.  The  medial 
surface  of  the  main  part  of  the  bone  presents  a  heavy  shelf  of  bone, 
the  sustentaculum  tali  the  plantar  surface  of  which  is  grooved  for  the 
tendons  of  the  m.  flexor  hallucis  longus.  Its  superior  surface  pre- 
sents the  middle  calcaneal  facet  (for  the  astragalus).  The  superior 
surface  of  the  main  portion  of  the  bone  presents  a  large  dorsal  cal- 
caneal facet  and  a  small  ventral  calcaneal  facet  in  front  of  the  middle 
one.  These  are  for  articulation  with  the  corresponding  facets  upon 
the  astragalus.  The  dorsal  facet  is  separated  from  the  others  by  a 
deep  groove  (sulcus  calcanei).  The  lateral  surface  is  somewhat  con- 
cave. The  ventral  extremity  is  a  concave  articular  facet  for  articula- 
tion with  the  scaphoid  (navicular)  bone. 


104 


.OSTEOLOGY 


Articulations. — With  the  astragalus  (talus)  and  the  scaphoid  (navicular)  hones. 

Muscles  Attached. — Origins. — Jim.  flexor  digitorum  brevis,  abductores 
hallucis  and  digiti  quinti.  flexor  quadratus  plants  and  extensor  digitorum  brevis. 

Insertions. — Mm.  plantaris,  tibialis  posterior  and  tendo  Achillis  (calcaneus) 
(eight). 

The  scaphoid  bone  (os  naviculare)  is  somewhat  concavoconvex. 
Its  proximal  (correctly  dorsal)  surface  is  a  concave  articular  facet 

f^  Pkatm i  ill  o/ digit  ii 

l'h,ilnni  II  a;  tllgft  ll 
I  9)  dipt  II 


FtG.  76. — A  frozen  preparation  of  the  bones 
of  the  foot  seen  from  the  plantar  surface. 
(Scholia  and  McMurrich.) 


Fig. 
McMu 


•    dorsal 
ch.) 


for  the  head  of  the  astragulus.  The  distal  (ventral)  surface  presents 
three  confluent  quadrate  facets  for  articulation  with  the  three 
cuneiform  bones.  The  medial  space  projects  as  the  tuberosity.  The 
other  surfaces  are  roughened. 


Articulations. — With  the  astragalus  and  three  cuneiform  bones  (four). 
Muscles  Attached.— M.  tibialis  posterior  (inserted). 


THE    METATARSI'S  IOj 

The  cuboid  (os  cuboideumj  is  laterally  placed  and  is  roughly 
cuboidai  in  form.  Its  medial  surface  presents  a  facet  for  articulation 
with  the  lateral  cuneiform  bone  and  occasionally  with  the  navicular 
bone.  The  proximal  surface  has  a  concave  facet  for  articulation  with 
the  calcaneum.  The  distal  surface  presents  two  articular  facets  for 
the  fourth  and  fifth  metatarsal  bones.  The  plantar  surface  bears  a 
groove  (sulcus  peronei)  for  the  tendon  of  the  m.  peroneus  longus. 

Articulations. — With  the  calcaneum,  lateral  cuneiform,  fifth  and  fourth  meta- 
tarsal bones  and  occasionally  with  the  navicular  bone. 
Muscle  Attached. — Origin. — M.  flexor  hallucis  brevis. 
Insertion. — Part  of  the  m.  tibialis  posterior. 

The  three  cuneiform  bones  are  wedge-shaped  and  form  with  the 
cuboid  the  distal  row  of  tarsal  bones. 

The  first  or  medial  cuneiform  bone  is  the  largest  and  articulates 
with  the  first  metatarsal  bone,  distally,  the  navicular,  proximally  and 
the  second  metatarsal  and  second  cuneiform  bones,  laterally. 

Muscles  Attached. — Mm.  tibialis  anterior,  tibialis  posterior  and  peroneus 
longus  (inserted). 

The  second  (middle)  cuneiform  bone  is  the  smallest.  It  articu- 
lates distally,  with  the  second  metatarsal  bone,  laterally,  with  the 
third  cuneiform  bone  and  medially,  with  the  first  cuneiform  and 
proximally  with  the  navicular  bone. 

Muscles  Attached. — Part  of  the  tendon  of  the  m.  tibialis  posterior  is  inserted. 

The  third  (lateral)  cuneiform  bone  articulates  distally  with  the 
third  metatarsal  bone  laterally  with  the  fourth  metatarsal  and 
cuboid,  proximally  with  the  navicular  and  medially  with  the  second 
cuneiform  and  second  metatarsal   bones. 

Muscle  Attached. — Origin. — M.  flexor  hallucis  brevis. 

Insertion. — M.  tibialis  posterior. 

Ossification. — The  tarsal  bones  are  of  endochondral  origin.  The  calcaneum 
develops  from  two  centers  and  the  others  from  one  each.  The  centers  appear  in 
the  following  order: 

Calcaneum  (body)  sixth  month  of  fetal  life 

Astragalus  (talus)  seventh  month  of  fetal  life 

Cuboid  ninth  month  of  fetal  life 

Lateral  cuneiform  first  year 

Medial  cuneiform  third  year 

Scaphoid  and  middle  cuneiform  fourth  year 

Tuberosity   of    the  calcaneum  about  the  tenth  year  and  fuses  with 
the  body  about  the  age  of  puberty. 

THE  METATARSUS 

The  metatarsus,  like  the  palm,  consists  of  Jive  bones.  Each 
presents  a  proximal  extremity  or  base,  a  shaft  and  a  distal  extremity,  or 
head.  The  proximal  extremities  articulate  with  the  distal  row  of 
tarsal  bones  and  with  each  other.    The  first  is  the  shortest  and 


Io6  OSTEOLOGY 

stoutest  and  the  second  the  longest.  The  fifth  presents  a  tuberosity 
at  the  lateral  part  of  the  proximal  extremity  to  which  the  tendon  of 
the  m.  peroneus  tertius  is  attached. 

Ossification. — These  are  of  endochondral  origin  and  each  develops  from  two 
centers,  one  for  the  shaft  and  one  for  the  digital  extremity  of  the  four  outer  meta 
tarsals  and  one  for  the  shaft  and  one  for  the  base  of  the  first  metatarsal.  The 
center  for  the  shaft  appears  during  the  ninth  week  of  fetal  life;  the  center  for  the 
base  of  the  first  metatarsal  appears  during  the  third  year;  the  centers  for  the 
distal  extremities  of  the  others  appear  between  the  fifth  and  eighth  years.  Fusion 
of  shaft  and  epiphysis  is  usually  completed  by  the  eighteenth  to  the  twentieth 
years. 

Muscles  Attached. — 
First  Metatarsal. — Origin. — First  dorsal  interosseous.     Insertions. — .Mm.  tibialis 

posterior,  peroneus  longus  (three). 
Second  Metatarsal. — Origin. — Mm.  adductor  hallucis  obliquus,  first  and  second 

dorsal     interossei.     Insertions. — Mm.    tibialis  posterior,  peroneus  longus 

(five). 
Third  Metatarsal. — Origins. — Mm.  adductor  obliquus  hallucis,  second  and  third 

dorsal   interossei,  first  plantar  interosseous.     Insertions. — M.  tibialis  pos- 
terior (five). 
Fourth  Metatarsal. — Origins. — Mm.  adductor  hallucis  obliquus,  third  and  fourth 

dorsal    interossei,   second    plantar    interosseous.     Insertions. — M.   tibialis 

posterior  (five). 
Fifth  Metatarsal. — Origins. — Mm.  flexor  quinti  digiti  brevis,  adductor  hallucis 

transversus.  fourth  dorsal  and  third  plantar  interossei.     Insertions. — Mm. 

peroneus  brevis  and  peroneus  tertius  (six). 

THE  PHALANGES 

The  phalanges  of  the  foot  resemble  those  of  the  hand  in  number, 
form  and  arrangement.  Their  nutrient  foramina  are  similar. 
Each  consists  of  a  proximal  extremity,  shaft  and  distal  extremity. 
Their  articulations  are  also  similar. 

Ossification. — These  are  of  endochondral  origin  and  each  is  developed  from 
two  centers.  The  center  for  the  shaft  appears  during  the  tenth  week  of  fetal  life 
and  those  for  the  proximal  extremities  appear  between  the  fourth  and  tenth  years. 
Fusion  between  these  parts  occurs  about  the  eighteenth  year. 

Muscles  Attached. — All  are  insertions. 
First  Phalanx   of  the  Great   Toe. — Mm.   extensor  digitorum  brevis   (innermost 

tendon),  abductor  hallucis.  adductores  hallucis  transversus  and  obliquus, 

flexor  hallucis  brevis  (five). 
First  Phalanx  of  the  Second  Toe. — First  and  second  dorsal  interossei,  first  lum- 

bricale  (three). 
First  Phalanx  of  Third  Toe. — Third  dorsal  interosseous,  first  plantar  interosseous, 

second  lumbricale  (three). 
First  Phalanx  of  the  Fourth   Toe. — Fourth  dorsal  interosseous,  second  plantar 

interosseous,  third  lumbricale  (three). 
First  Phalanx  of  the  Little  Toe. — Mm.  flexor  digitorum  quinti  brevis,  abductor 

digiti  quinti  brevis,  third  plantar  interosseous,  fourth  lumbricale  (four). 
Second  Phalanx  of  the  Great  Toe. — Mm.  extensor  hallucis  longus,  flexor  hallucis 

longus  (two). 


THE    FOOT    AS    A    WHOLE 


107 


Second  Phalanx  of  the  Other  Toes. — Mm.  flexor  digitorum  brevis,  one  slip  of  the 
common  tendon  of  the  extensor  digitorum  longus  and  the  extensor  digitorum 
brevis  (except  the  fifth  toe). 

Third  Phalanges. — Two  slips  of  the  common  tendon  of  the  extensor  digitorum 
longus,  the  extensor  digitorum  brevis  and  flexor  digitorum  longus. 

THE  FOOT  AS  A  WHOLE 

The  bones  of  the  foot  are  arranged  in  the  form  of  an  arch  and  this 
supports  the  weight  of  the  body  in  the  erect  position.  The  foot  is 
placed  at  a  right  angle  to  the  leg.  There  are  two  arches,  longitudinal 
and  transverse. 


Tarsus     Sinus  ft 


Navicular  bonr 

Middle  cuneiform  bone 
/         External  cuneiform  bone 


calcaneus 

-A  frozen  preparation  of  the  bones  of  the  right  foot  : 
(Sobctie.  and  McMun 


1  from  the  outer  side. 


The  longitudinal  arch  is  the  larger  and  the  longer;  the  curvature 
of  the  arch  is  greater  on  the  medial  aspect  than  it  is  on  the  lateral 
aspect.  The  heel  (back)  part  of  the  arch  is  made  up  of  the  calcaneum 
and  the  proximal  part  of  the  astragalus  and  is  about  3  inches  in 
length;  the  front  part  of  the  arch  consists  of  the  other  tarsal  and  the 
metatarsal  bones  and  measures  about  7  inches  in  length.  The 
weakest  part  of  the  arch  is  at  the  joint  between  the  astragalus  and 
scaphoid  bones.  It  is  especially  supported  here  by  ligaments  (the 
calcaneoscaphoid  and  the  tendon  of  the  m.  tibialis  posterior). 
Whenever  these  give,  the  arch  becomes  lower  and  causes  Hat-foot. 

The  transverse  arch  of  each  foot  is  only  a  half  arch  and  the  whole 
is  formed  when  the  two  feet  are  placed  in  apposition.  This  half 
arch  represents  the  difference  in  height  of  the  longitudinal  arch  at 
its  lateral  and  medial  aspects. 


CHAPTER  II 

SYNDESMOLOGY 

THE    JOINTS 

A  joint,  when  movable,  is  the  fulcrum  at  which  the  levers  (bones) 
are  moved  by  the  muscles.  There  are  two  main  divisions  of  joints, 
the  immovable  and  the  movable. 

i.  Synarthroses,  or  immovable  articulations,  are  those  in  which 
no  motion  is  perceptible.  In  these  the  apposed  edges  of  the  bones 
are  irregular  and  fit,  or  dove-tail,  into  one  another.  There  is  a 
small  amount  of  white  fibrous  tissue  separating  the  bones,  but  no 
joint  cavity  exists.     There  are  four  varieties. 

(a)  Suture  (sutura)  is  that  form  found  in  the  skull.  •  When  the 
irregularities  of  the  connecting  bones  are  well  marked  they  form  a 
true  suture  (sutura  vera),  otherwise  a  false  suture  (sutura  notka). 
When  the  sutural  projections  are  tooth-like  they  form  a  sutura 
dentata;  when  saw-like  they  constitute  a  sutura  serrata;  when 
ridge-like  they  form  a  sutura  limbosa.  The  false  suture  may  be 
a  sutura  squamosa  (squamoparietal),  a  sutura  harmona  (palatal 
processes  of  the  maxillae). 

(b)  Schindylesis  is  that  variety  in  which  a  bone  is  placed  in  a 
cleft  between  two  lamellae  of  another,  as  the  articulation  of  the 
vomer  with  the  maxilla1. 

(c)  Gomphosis  is  that  form  in  which  a  conical  process  fits  into  a 
special  socket,  as  the  articulation  of  the  teeth  with  the  mandible 
and  maxillae. 

(d)  Synchondrosis  is  that  variety  in  which  hyalin  cartilage 
intervenes  between  the  articular  surfaces  of  certain  bones,  early 
in  life,  to  be  later  ossified.  This  is  represented  by  the  epiphyseal 
cartilage  separating  shaft  and  extremities  of  long  bones,  before  adult 
life. 

Movable  joints  comprise  two  classes,  partly  movable,  or  amphi- 
arthroses  and  freely  movable,  or  diarthroses. 

i.  Amphiarthroses  exhibit  slight  movement  and  they  resemble 
somewhat  in  structure  the  diarthroses.     Two  varieties  are  noted. 

(a)  Symphysis,  that  form  in  which  the  two  articular  surfaces  of 
the  bones  are  connected  by  an  intervening  plate  of  fibrocartilage. 
All  parts  are  held  together  by  ligaments  and  a  rudimentary  joint 
cavity  may  be  present.  Examples  are  the  symphysis  pubis  and  the 
articulations  between  the  bodies  of  the  true  vertebrae. 
1 08 


STRUCTURE    OF    A    JOINT  IOq 

(b)  Syndesmosis,  that  form  in  which  the  bony  surfaces  are  con- 
nected by  an  interosseous  ligament,  as  the  inferior  tibiofibular 
articulation. 

2.  Diarthroses. — Most  of  the  articulations  come  under  this  class 
and  a  number  of  varieties  are  given. 

(a)  Arthrodia  is  that  variety  in  which  there  is  a  somewhat  limited 
gliding  movement,  as  between  the  bones  of  the  carpus,  the  tarsus 
and  the  articular  processes  of  the  vertebra. 

(b)  Ginglimus,  or  hinge  joint,  is  that  form  in  which  motion  occurs 
only  in  one  plane,  that  is  at  right  angles  to  the  long  axis  of  the  bones 
taking  part  (as  in  a  hinge).  The  best  examples  are  the  interpha- 
langeal  articulations  and  the  elbow  joint.  The  knee  and  ankle 
joints  belong  to  this  variety  but  permit  of  some  lateral  movement. 

(c)  Condyloid,  or  biaxial  articulations,  permit  of  movement  in 
two  planes,  at  right  angles  to  each  other,  permitting  flexion,  exten- 
sion, abduction  and  adduction  and  circumduction,  as  in  the 
radiocarpal  articulation. 

((/)  Trochoid,  or  rotary  joint,  is  that  variety  iri  which  there  is 
rotation  only,  as  in  the  proximal  and  distal  radioulnar  articulations, 
as  well  as  that  between  the  dens  of  the  epistropheus  with  the  atlas 
and  transverse  ligament. 

(c)  Reciprocal  reception,  or  saddle  joint,  is  a  term  applied  to  the 
carpometacarpal  articulation  of  the  thumb.  Such  permits  of 
flexion,  extension,  abduction,  adduction  and  circumduction. 

(/)  Enarthrosis,  or  ball  and  socket  joint,  is  the  variety  that  per- 
mits of  motion  about  practically  any  number  of  axes  from  a  common 
center,  as  the  hip  and  the  shoulder  joints. 

A  number  of  structures  are  required  in  order  to  have  a  diarthrodial  joint,  as 
bones,  cartilage,  ligaments  and  synovial  membrane.  Two  bones  are  necessary 
and  their  articular  surfaces  are  so  formed  and  adapted  to  each  other  so  as  to 
permit  of  certain  movements.  The  parts  of  these  bones  that  actually  rub  against 
each  other  are  covered  with  a  layer. of  hyalin  cartilage.  Ligaments  connect 
the  bones  together  so  as  to  prevent  them  from  separating.  A  synovial  membrane 
lines  the  inner  surface  of  the  capsular  ligament  and  covers  all  parts  of  the  bones 
within  the  joint  cavity  except  that  part  covered  with  hyalin  cartilage  (real  articular 
surfaces). 

The  structure  of  bone  has  been  discussed  in  the  chapter  on  "Osteology." 

Cartilage. — There  are  three  varieties:  (a)  hyalin,  (b)  fibrocartilage, 
(c)  elastic  cartilage. 

Cartilage  is  surrounded  by  an  investing,  genetic  membrane  called 
the  perichondrium,  which  is  analogous  to  the  periosteum  of  bones. 
From  it  the  cartilage  cells,  or  chondroblasts,  arise.  Within  the  peri- 
chondrium is  the  matrix  containing  the  cartilage  cells.  In  hyalin 
cartilage  this  matrix  is  apparently  homogeneous.  In  special  prepa- 
rations, however,  a  groundwork  of  white  fibrous  tissue  may  be 
recognized.     The   cartilage   cells    beneath    the    perichondrium    are 


110  SYNDESMOLOGY 

small,  elongated  and  close  together.  Near  the  middle  of  the  cartilage 
they  are  larger,  oval  and  each  usually  lies  in  a  distinct  space,  or 
lacuna. 

Hyalin  cartilage  is  found  covering  the  articular  surfaces  of  bones, 
and  as  the  costal,  tracheal,  bronchial  and  the  larger  laryngeal  car- 
tilages.    It  may  calcify  or  even  ossify. 

In  fibrocartilage  the  matrix  is  chiefly  white  fibrous  tissue  in  which 
the  fibers  are  mostly  parallel  to  one  another.  The  cartilage  cells  lie 
in  little  scattered  islands  of  hvalin  matrix. 


T^ 


J    -r 


■-■■■     :     —- 


B 


C 


Fig.  79. — Sections  of  cartilage.  A.  Hyalin  cartilage,  a.  Fibrous  layer  of  peri- 
chondrium; 6,  genetic  layer  of  perichondrium;  c,  youngest  chondroblasts;  d,  older  chondro- 
blasts;  e,  capsule;  /,  cells;  g,  lacuna.  B.  Elastic  cartilage.  C.  White  fibro-cartilage. 
(Radasch's  Histology.) 


Fibrocartilage  is  found  as  the  intervertebral  discs,  interarticular 
cartilages  and  deepening  joint  cavities.     It  may  calcify  in  old  age. 

Elastic  cartilage  does  not  concern  us  here. 

Ligaments  are  those  bands  of  dense  white  fibrous  tissue  that  hold 
the  bones  together.  They  resemble  the  fascia?  in  structure  and  con- 
sist of  bundles  of  white  fibrous  tissue,  most  of  which  are  parallel  to 
one  another;  other  bundles  pass  obliquely  or  transversely  to  the 
preceding  and  bind  all  together  into  a  firm  sheet  or  band.  A  variable 
quantity  of  elastic  tissue  is  present.  The  connective-tissue  cells  lie 
between  the  bundles  of  fibers  and  are  comparatively  few  in  number. 
Ligaments  are  whitish  and  shiny  in  appearance  and  are  arranged  as 


STRUCTURE    OF    A    JOINT  III 

capsules  with  accessory  strengthening  portions,  or  as  individual 
bands  or  intraarticular  ligaments. 

A  synovial  membrane  is  a  thin,  delicate  serous  membrane  that  lines 
the  joint  cavity.  It  consists  of  a  single  layer  of  endothelial  cells  that 
are  flat  and  plate-like  with  irregular  edges  that  fit  into  one  another. 
At  intervals  small  gaps  or  stomata  exist.  These  cells  rest  upon  a  thin 
layer  of  fibroelastic  subendothelial  tissue.  This  membrane  does  not 
extend  over  the  hyalin  cartilage  of  the  articular  surfaces  in  the  adult. 
These  membranes  transude  {not  secrete)  a  thick,  viscid  substance, 
called  synovia,  that  lubricates  the  joint.  Synovial  membranes  are 
found  elsewhere  as  in  bursae,  and  vaginal  synovial  membranes. 

Bursae  are  sacs  of  white  fibrous  tissue  lined  with  a  synovial  mem- 
brane; they  may  be  cutaneous,  as  those  placed  between  the  skin 
and  a  prominent  bony  process  (over  the  patella,  olecranon  and 
malleoli).  The  subtendinous  bursee  are  those  intervening  between 
a  tendon  and  a  bone  or  cartilage,  facilitating  the  action  of  the  muscle. 
Some  bursae  are  over  joints. 

A  vaginal  synovial  membrane  (synovial  sheath)  is  one  that  lines 
a  groove  or  canal  in  the  bone,  through  which  a  tendon  passes,  thus 
facilitating  its  action.  These  are  seen  in  connection  with  the  flexor 
and  extensor  tendons  of  the  fingers  and  toes,  especially. 

ARTICULATIONS  OF  THE  VERTEBRAL  COLUMN  AND  HEAD 

The  articulations  of  the  vertebral  column  are  those  between  the 
bodies  and  those  between  the  articular  processes.  In  addition  there 
are  ligaments  connecting  the  spinous  processes,  transverse  processes 
and  laminae. 

Bodies. — These  articulations  are  amphiarthrodial  and  the  liga- 
ments are  intervertebral,  ventral  longitudinal  and  dorsal  longitudinal. 

The  intervertebral  discs  vary  in  thickness  in  the  various  parts  of  the 
vertebral  column.  Each  conforms  in  shape  to  the  surfaces  of  the 
bodies  to  which  it  is  firmly  attached.  Its  peripheral  portion  (annu- 
lus fibrosus)  is  dense  and  tough  white  fibrocartilage,  while  its  central 
portion  {nucleus  pulposus)  is  soft,  pulpy  and  elastic. 

The  ventral  longitudinal  ligament  (lig.  longitudinale  anterius)  is  a 
broad,  fibrous  band  that  extends  from  the  epistropheus  to  the 
superior  segment  of  the  sacrum.  It  is  attached  to  the  projecting 
superior  and  inferior  edges  of  the  ventral  portion  of  each  body  and  the 
intervertebral  disc.  Some  of  its  fibers  are  of  short  course  and  others 
extend  over  three  or  four  vertebrae. 

The  dorsal  longitudinal  ligament  (lig.  longitudinale  poster ius)  con- 
nects the  dorsal  surfaces  of  the  bodies  in  the  same  manner.  It  lies 
in  the  vertebral  canal. 

Articular  Processes. — The  articular  processes  form  arlhrodial 
articulations.     Each  contiguous  pair  of  processes  is  surrounded  by 


SYXDESMOLOGY 


Fig.  80. — The  ventral  longitudinal  lig- 
ament in  the  lower  thoracic  portion  of 
the  vertebral  column,  together  with  the 
costo-vertebral  ligaments  seen  from  in 
front.     (Sobotta  and  McMurrich.) 


Fig.  81.— The  dorsal  longitudinal  liga- 
ment in  the  lower  thoracic  and  upper 
lumbar  portions  of  the  vertebral  column. 
The  vertebral  arches  have  been  removed. 
(Sobotta  and  McMurruh.) 


Inten-ertebral  foramen 


Intervertebral  fibrocartitage 


Fig.  82. — Two  thoracic  vertebrae  divided  longitudinally  in  the  medu 
ligamenta  flava.      {Sobotta  and  McMurrn  In 


and  showing  the 


LIGAMENTS    OF    THE    VERTEBRAL    COLUMN  II3 

a  thin  capsular  ligament  (capsula  articularis)  that  is  usually  com- 
pleted by  the  ligamenta  flava.  These  ligaments  are  loosest  in  the 
cervical  region,  where  movement  is  most  extensive,  and  are  attached 
to  the  bone  adjoining  the  articular  surfaces. 

Other  ligaments  are  as  follows: 

Ligamenta  Flava. — The  laminae  of  adjoining  vertebrae  are  connected 
to  each  other  by  the  short,  yellow,  elastic  ligamenta  flava.  These 
close  in  gaps  in  the  osseous  vertebral  canal. 

Ligamenta  intertransversaria  are  short  ligaments  that  connect  the 
transverse  process  of  the  vertebrae,  except  in  the  cervical  and  upper 
thoracic  region. 

Ligamenta  supraspinaUa  form  a  strong  band  that  connects  the 
tips  of  the  spinous  processes  together.  In  the  neck  it  is  usually 
more  highly  developed  and  consists,  mainly,  of  yellow  elastic  tissue. 
This  part  is  called  the  ligamenlum  nucha  and  is  important  and  highly 
developed  in  quadrupeds. 

Ligamenta  inter spinalia  are  the  short,  thin  bands  that  connect 
one  spine  with  another,  and  extend  dorsoventrally  from  the  supra- 
spinous ligaments  to  the  ligamenta  flava. 

The  lumbosacral  articulation  is  similar  to  that  of  the  typical 
vertebrae.  Two  accessory  lumbosacral  ligaments  are  present.  Each 
extends  from  the  transverse  process  of  the  last  lumbar  vertebra  to 
the  ventral  aspect  of  the  ala  of  the  sacrum;  occasionally  there  is  an 
extension  from  the  lateral  part  of  the  body  of  the  last  lumbar  ver- 
tebra to  each  ala. 

The  sacrococcygeal  articulation  is  a  symphysis.  The  last  seg- 
ment of  the  sacrum  and  the  first  of  the  coccyx  are  connected  by 
strong  ventral,  dorsal  and  lateral  sacrococcygeal  ligaments.  An 
intervetebral  Jibrocartilage  is  present. 

The  vertebral  column  is  capable  of  flexion,  extension,  lateral  flexion, 
rotation  and  some  circumduction.  The  movements  are  most  exten- 
sive in  the  cervical  and  lumbar  regions  and  while  the  movement  of 
one  vertebra  upon  its  neighbor  may  be  small,  the  motion  as  a  whole 
becomes  considerable. 

ATLAS  AND  AXIS 

This  articulation  (atlantoepistrophica)  comprises  those  of  the 
articular  processes  and  that  between  the  dens  and  atlas. 

The  articulation  between  the  processes  are  arthrodial.  Each 
joint  possesses  a  capsular  ligament  and  an  accessory  ligament;  the 
latter  is  located  in  the  vertebral  canal  and  represents  a  thickening 
of  the  capsular  ligament. 

The  ventral  atlantoepistropheal  ligament  connects  the  ventral  sur- 
face of  the  body  of  the  epistropheus  to  the  ventral  surface  of  the 
ventral  arch  of  the  atlas.     This  is  reinforced  bv  the  fibers  of  the 


H4 


SYXDESMOLOGY 


ventral  longitudinal  ligament.  The  dorsal  atlantoepistropheal  liga- 
ment extends  from  the  dorsal  arch  of  the  atlas  to  the  lamina;  of  the 
epistropheus  (like  a  ligamentum  flavum). 

The  transverse  ligament  (lig.  transversum  atlantis)  extends  trans- 
versely between  the  two  tubercles  of  the  atlas  and  dorsal  to  the 
neck  of  the  dens  of  the  epistropheus;  between  these  two  structures 
there  exists  a  synovial  sac.  The  cruciform  ligament  (lig.  cruciatum 
atlantis)  is  formed  by  the  transverse  ligament  sending  fibers  from 
its  superior  margin  to  the  ventral  margin  of  the  foramen  magnum 

Alar         Cmriatt  ligament 


Fig.  83. — The  atlanto-odontoid  articula- 
tion. The  odontoid  process  {den,  epis- 
trophei) and  the  ventral  arch  of  the  atlas 
have  been  cut.     (Sobotla  and  McMurrich.) 


Fig.  84. — The  cruciate  ligament  after  re- 
moval of  the  tectorial  membrane.  The  artic- 
ular capsules  have  also  been  removed  on  the 
right  side.     (Sobolla  and  McMurrich.) 


and  fibers  from  its  inferior  margin  to  the  dorsal  surface  of  the  body 
of  the  axis. 

Movements. — The  head  and   the  atlas  rotate  upon   the  axis  or 
epistropheus. 


ATLAS  AND  OCCIPITAL  BONE 

The  atlantooccipital  articulation   (articnlatio  atlantooccipitalis)  is 

a  d  {arthrosis.     The  ligaments  are  as  follows: 

1.  A  capsular  ligament  that  surrounds  each  condyle  of  the 
occipital  bone  and  corresponding  facet  of  the  atlas. 

2.  The  ventral  atlantooccipital  membrane  imcmbrana  atlantooccip- 
italis anterior)  extends  from  the  ventral  arch  of  the  atlas  to  the 
ventral  margin  of  the  foramen  magnum  and  is  thickened  in  the 
median  line. 

3.  The  dorsal  atlantooccipital  membrane  extends  from  the  dorsal 
arch  to  the  dorsal  margin  of  the  foramen  magnum.  Both  are 
continuous  with  the  capsular  ligaments. 

4.  The  alar,  or  check,  ligaments  (ligg.  alaria)  are  two  short,  strong 


THE    MANDIBULAR    ARTICULATION  115 

oords  extending  right  and  left  from  the  sides  of  the  apex  of  the  dens 
to  the  condylar  portions  of  the  occipital  bone. 

5.  The  ligament  of  the  apex  (lig.  apicis  dentis)  extends  from  the 
apex  of  the  dens  to  the  ventral  margin  of  the  foramen  magnum. 

Occipital  bone 


Fig.  85. — A  portion  of  the  occipital  bone  together  with  the  atlas  and  axis  (epistropheus) 
and  their  ligaments  seen  from  behind.  On  the  left  side  the  capsule  of  the  atlanto- 
epistropheal  articulation  has  been  removed.     (Sobotta  and  McXIurrkh.) 

Movements. — Between  the  occipital  bone  and  the  atlas,  a  rocking 
motion  is  accomplished  (nodding)  as  well  as  a  limited  amount  of 
oblique  motion. 

THE  MANDIBULAR  ARTICULATION 

The  mandibular  articulation  {articulatio  mandibularis)  is  a 
ginglymo-arthrosis  and  the  parts  concerned  are  the  condyles  of  the 
mandible  and  the  mandibular  fossa;  of  the  temporal  bones.  An 
intraarticular  cartilage  (disc)  intervenes  between  these  bones,  however. 

1.  The  loose  capsular  ligament  is  attached  to  the  edges  of  the 
fossa  and  to  the  neck  of  each  condyle. 

2.  The  temporomandibular  ligament  (lig.  tern poromandibulare)  is  a 
vthickening  of  the  lateral  wall  of  the  capsule  and  extends  between 

the  inferior  margin  of  the  zygoma  and  the  neck  of  the  mandible 
(dorsally  and  laterally). 

3.  The  articular  disc  (discus  articularis)  is  a  concavo-convex  mass 
of  fibrocartilage  that  is  attached,  peripherally,  to  the  capsule  so  as 
to  divide  the  joint  cavity  into  two  compartments,  each  of  which 
has  its  own  synovial  membrane. 

4.  The  sphcnomandibular  ligament  (lig.  sphenomandibulare)  is  a 
thin,  fiat  band  extending  between  the  spine  of  the  sphenoid  bone  and 
lingula  of  the  mandible.     It  is  an  accessory  ligament. 

5.  The  stylomandibular  ligament  (lig.  stylomaudibulare)  extends 
from  the  styloid  process  of  the  temporal  bone  to  the  dorsal  margin 
of  the  angle  of  the  mandible.     It  is  an  accessory  ligament. 

Movements. — Depression,  elevation,  forward,  backward,  lateral 
(grinding). 


n6 


SYXDESMOLOGY 


ARTICULATIONS  OF  THE  THORAX 

Two  articulations  exist  between  each  rib  and  the  vertebral  column. 
The  head  articulates  with  the  bodies  and  the  tubercle  with  a  transverse 
process. 

COSTOVERTEBRAL  ARTICULATIONS 

The  articulations  of  the  heads  of  the  ribs  (articulatianes  capitu- 
lorum)  are  of  the  ginglynwid  variety  of  diarthrosis.     The  head  articu- 


remporomamiibuLir  ligament 

Zygomatic  arch 


Pterygoid  process 

Temporal  bone 

Sphenoid  bone 

/    Sphertot.nindt- 

1 

butar  ligament 

Fig.  86. — The  right  temporomandib- 
ular articulation  seen  from  the  outer 
side.,     (Sobotta  and  McMurrich.) 


Fig.  87. — The  right  temporo-mandibu- 
lar  articulation  seen  from  the  inner  side. 
{Sobotta  and  McMurrich.) 


lates  with  the  demifacet  of  the  two  adjoining  vertebral  bodies. 
A  capsular  ligament  surrounds  these  parts.  The  ventral  portion  of 
the  capsule  is  reinforced  by  three  radiating  bundles  of  fibers  called 
the  radiate  ligaments  of  the  head  (fig.  capituli  costce  radiation). 
These  start  at  the  head;  the  middle  one  is  attached  to  the  inter- 
vertebral disc  and  the  others  to  the  vertebral  bodies. 

The  intraarticular  ligament  (lig.  capituli  costce  intraarticulare)  is 
within  the  joint;  it  is  attached  to  the  ridge  on  the  head,  between  the 
two  facets,  and  to  the  intervertebral  disc. 


ARTICULATION    OF    THE    RIBS 


117 


The  costotransverse  articulations  {articidationes  coslotransversarice) 
of  the  typical  ribs  are  those  between  the  tubercles  of  the  ribs  and 
the  transverse  processes  of  the  lower  vertebra  with  which  the  head 


articulates.     These   are   arthrodial  joints.     The   capsular   ligament 
is  thin  but  is  not  found  on  the  eleventh  and  twelfth  ribs. 

The  ventral  costotransverse  ligament   {Kg.  costotransversarium  an- 
terior) is  short  and  strong;  it  connects  the  neck  and  tubercle  of  the 


n8 


^VNDKSMOLOGY 


rib  with  the  transverse  process  above  and  to  its  costotransverse 
capsular  ligament. 

The  dorsal  costotransverse  ligament  is  a  short  and  oblique  fasciculus 
that  connects  the  transverse  process  with  the  nonarticular  portion 
of  the  tubercle.  Such  ligaments  are  absent  on  the  eleventh  and 
twelfth  ribs. 

The  ligament  of  the  neck  of  the  rib  (lig.  colli  costce)  consists  of  short 
fibers  that  connect  the  dorsal  surface  of  the  neck  with  the  ventral 
surface  of  the  transverse  process,  though  some  of  the  fibers  pass  to 
the  inferior  articular  process  of  the  upper  vertebra. 

STERNOCOSTAL  ARTICULATIONS 

The  articulations  of  the  costal  cartilages  of  the  true  ribs,  except 
the  first,  are  of  the  arthrodial  variety. 


i 


i 


■• '  A/ 


Fir..   90. — A  frontal  longitudinal  section  of  the  sternum  and  costal  cartilages.      (Sobotta  and 
.1/,  Murrich.) 


A  thin  capsular  ligament  surrounds  each  joint. 

The  ventral  sternocostal,  or  radiate  ligaments  pass  from  the  ventral 
surfaces  of  the  costal  cartilages  to  the  ventral  surface  of  the  sternum, 
interlacing  with  those  of  the  opposite  side  forming  the  membrana 
sterni. 


STERNOCLAVICULAR    ARTICULATION  IIQ 

The  dorsal  sternocostal  ligaments  are  like  the  preceding  but  less 
prominent. 

The  intraarticular  sternocostal  ligaments  (Jig.  sternocostal  intra- 
articulare)  are  inconstant  in  all  except  the  second  sternocostal  articu- 
lation. When  these  are  present,  they  extend  transversely  between 
the  costal  cartilage  and  the  sternum  and  divide  the  joint  cavity 
into  two  distinct  (superior  and  inferior)  portions. 

The  xiphoid  ligament  passes  from  the  ventral  surface  of  the  xiphi- 
sternum  to  the  ventral  surface  of  the  seventh  and  sometimes  the 
sixth  costal  cartilage. 

INTERCHONDRAL  ARTICULATIONS 

The  cartilages  of  the  sixth,  seventh  and  eighth  (ninth  and  tenth 
sometimes)  ribs  articulate  with  each  other  forming  arlkrodial  joints. 
Each  joint  is  surrounded  by  a  thin  capsule.  The  ventral  and  dorsal 
portions  of  the  capsule  are  thickened  by  fibers  connecting  the 
adjacent  cartilages.  These  constitute  the  external  and  internal 
inter  chondral  ligaments. 

Each  costal  cartilage  fits  into  a  depression  on  the  sternal  end  of 
the  shaft  of  a  rib.  There  is  no  true  joint  as  these  structures  are 
held  together  by  the  blending  of  the  periosteum  and  perichondrium. 

ARTICULATIONS   OF   THE   STERNUM 

The  sternal  synchondrosis  is  the  amphiarthrodial  articulation 
between  the  manubrium  and  body  of  the  sternum.  Ventrally  and 
dorsally  are  found  the  interstemal  ligaments  supported  by  the 
membrana  sterni. 

THE  ARTICULATIONS  OF  THE  SUPERIOR  EXTREMITY 

The  superior  extremity,  or  pectoral  appendage  comprises  the 
pectoral  girdle  (clavicles  and  scapula;)  and  the  appendages  proper. 
The  pectoral  girdle  articulates  with  the  axial  skeleton  ventrally,  only, 
at  the  sternum.  Each  clavicle  articulates  with  its  corresponding 
scapula. 

THE  STERNOCLAVICULAR  ARTICULATION 

The  sternoclavicular  articulation  (articulatio  sternoclavictdaris)  is 
of  the  arthrodial  variety.  The  parts  concerned  are  the  enlarged 
sternal  end  of  the  clavicle,  a  facet  upon  the  superolateral  angle  of  the 
manubrium,  the  superior  surface  of  the  first  rib  and  an  intraarticular 
fibrocartilage. 

A  capsular  ligament  encloses  the  joint. 

The  intraarticular  cartilage  (discus  intraarticularis)  is  thinner  in 
the  middle  than  at  its  circumference.     It  is  attached  peripherally 


120  SYNDESMOLOGY 

to  the  capsular  ligament,  as  well  as  to  the  clavicle  superiorly  and 
the  first  costal  cartilage  inferiorly. 

The  ventral  sternoclavicular  ligament  {lig.  sternoclavicular e  anterius) 
consists  of  fibers  strengthening  the  capsule  and  connecting  the 
ventral  surfaces  of  the  clavicle,  sternum  and  first  costal  cartilage. 

The  dorsal  sternoclavicular  ligament  is  similar  to  the  preceding. 

The  interclavicular  ligament  (lig.  interclavicularc)  is  a  strong  acces- 
sory ligament  connecting  the  sternal  ends  of  the  two  clavicles  across 
the  interclavicular  notch;  this  ligament  is  attached  to  the  upper 
margin  of  the  sternum  also. 


Costoclavicular 
ligament 
Articular  capsule 

Costal  cartilage  I  — " 


Costal  cartilage  II 


Sternal  synchondrosis 


Fig.  91. — The  two  sternoclavicular  joints,  together  with  the  costosternal  articulations  of 
the  two  upper  ribs  seen  from  in  front.  The  right  sternoclavicular  joint  has  been  opened  by  a 
saggital  section.      (Sobclta  and  McMurrich.) 

The  costoclavicular  ligament  (lig.  costoclaviculare),  also  accessory, 
is  a  strong,  oblique  band  connecting  the  first  costal  cartilage  with 
the  inferior  aspect  of  the  sternal  end  of  the  clavicle. 


THE  ACROMIOCLAVICULAR  ARTICULATION 

The  acromioclavicular  articulation  (articulalio  acromioclavicul- 
aris)  is  also  an  arthrodial  joint. 

A  capsular  ligament  is  present. 

The  superior  and  inferior  acromioclavicular  ligaments  are  thickened 
portions  of  the  capsule  connecting  adjoining  portions  of  the  clavicle 
and  acromion  of  the  scapula. 

An  intraarticular  cartilage  is  inconstant  and  when  present  it  is 
obliquely  placed  and  is  attached  by  its  circumference  to  the  capsule. 

The  coracoclavicular  ligament  (lig.  coracoclavicularis)  is  an  acces- 
sory ligament  and  connects  the  coracoid  process  of  the  scapula  and 
the  acromial  end  of  the  clavicle;  it  consists  of  two  parts. 


THE    SHOULDER    JOINT 


The  trapezoid  ligament  (lig.  trapezoidcum)  is  attached,  inferiorly, 
to  the  basal  half  of  the  superior  surface  of  the  coracoid  process  and 
superiorly  to  the  inferior  surface  of  the  acromial  end  of  the  clavicle. 

The  conoid  ligament  (lig.  conoideum)  is  somewhat  triangular;  its 
blunt  apex  is  attached  to  the  base  of  the  coracoid  process  (near  the 
scapular  notch)  and  its  base  is  attached  to  the  coracoid  tuberosity  of 
the  clavicle.     It  lies  medial  to  the  preceding  ligament. 


Coracoclav  cular  ligament 
(Conoid  portion) 
Superior  transverse  ligament 


Coracoelavicalar  ligament  (Trapezoid  portion) 
Coracoid  process 

Coraco-acromial  ligament 
Acromion 


\     ,  Intertubercular  mucous 


^    Long  head  of  biceps 


-The  left  shoulder  and  acromioclavicular  joints  seen  f 
inner  surface.     (Sobotta  and  McMurrich.) 


above  and  from  the 


The  scapula  has  several  intrinsic  ligaments  that  are  not  articular. 
The  coracoacromial  ligament  (lig.  coracoacromialc)  is  attached,  in- 
feriorly, to  the  apical  half  of  the  dorsolateral  margin  of  the  coracoid 
process  and,  superiorly,  to  the  tip  of  the  acromion.  It  is  tense  and 
tends  to  protect  the  shoulder  joint. 

The  superior  transverse  ligament  (lig.  transversum  scapula:  superius) 
bridges  the  scapular  notch. 

The  inferior  transverse  scapular  ligament  connects  the  lateral 
margin  of  the  scapular  spine  with  the  dorsal  aspect  of  the  head  of 
the  scapula. 

THE  SHOULDER  JOINT  (ARTICULATIO  HUMERI) 

The  shoulder  joint  is  of  the  enarthrodial  variety  and  permits  of  the 
widest  range  of  movement  of  any  joint  of  the  body.  It  is  formed  by 
the  glenoid  fossa  of  the  scapula  and  the  head  of  the  humerus. 


122  SYNDESMOLOGY 

The  glenoid  ligament  (labrum  glenoidale)  is  a  ring-like  mass  of 
dense  white  fibrous  tissue  that  deepens  the  glenoid  fossa.  It  is 
firmly  attached  to  the  margin  of  that  fossa. 

The  capsule  (capsula  articularis)  is  attached,  proximally,  to  the 
circumference  of  the  glenoid  fossa  and  the  labrum  glenoidale;  distally 
it  is  attached  to  the  anatomical  neck  of  the  humerus.  It  is  strongest 
superiorly.  It  is  strengthened  by  fusion  with  the  tendons  of  the 
mm.  subscapularis,  supraspinatus  and  infraspinatus,  near  their 
insertions. 

The  transverse  humeral  ligament  is  a  portion  of  the  capsular  liga- 
ment that  bridges  the  groove  between  the  tubercles  of  the  humerus. 

Acromioclavicular  ligament 
Coraco-acromial  ligament 
Supraspinal 

1 


Fig.  93. — The  left  shoulder  joint  seen  from  behind,  the  long  head  of  the  triceps  being 
cut  and  the  terminal  portions  of  the  supraspinatus,  infraspinatus,  and  teres  minor  muscles 
cut  and  turned  outward.     (Sobolta  and  McMurrick.) 

The  coracohumeral  ligament  (lig.  coracohumerale)  is  an  accessory 
ligament  that  extends  the  base  of  the  coracoid  process  and  the  base 
of  the  greater  tubercle  of  the  humerus.  It  is  partially  fused  with 
the  capsular  ligament. 

The  glenoJiumeral  ligament  consists  of  three  bands  of  fibers  that 
strengthen  the  ventral  part  of  the  capsule  and  are  seen  only  upon  its 
inner  aspect.  They  extend  from  the  ventral  margin  of  the  glenoid 
fossa  to  the  ventral  part  of  the  neck  of  the  humerus. 

The  head  of  the  humerus  is  held  against  the  glenoid  fossa  by  mus- 
cular action  and  atmospheric  pressure  as  the  ligaments  themselves 
are  too  lax  to  do  this. 

The  synovial  membrane  lines  the  capsule  and  extends  over  the 
nonarticular  portions  of  the  bones  within  the  capsular  ligament. 
The  proximal  end  of  the  tendon  of  the  long  head  of  the  m.  biceps 
brachii  arise  within  and  passes  through  the  joint  cavity  and  leaves 


THE    ELBOW    JOIN  1 


123 


at  the  groove  between  the  tubercles.  The  tendon  is  enclosed  within 
the  synovial  membrane  which  is  prolonged  upon  it  into  the  groove 
but  the  cavity  here  is  closed.  Where  the  subscapularis  tendon  lies 
over  the  capsule  there  is  a  bursa  and  its  cavity  and  synovial  mem- 
brane are  continuous  with  the  joint  cavity.  The  subdeltoid,  or 
subacromial  bursa  does  not  communicate  with  the  joint  cavity. 

Movements. — This  joint  is  capable  of  flexion,  extension,  abduction, 
adduction,  rotation  and  circumduction. 


Tendon  of  iong  fiend  of  biceps 


Coracohumeral  ligament 


Inteiiubereular  mucous  shealh 


Tendon  of  long  head  of  biceps 


Fig.   04. — A  frontal  longitudinal  section  of  the  shoulder  joint,  parallel  to  the  tendon  of 
the  long  head  o!  5  Jwlla  and  McMurrich.) 

THE  ELBOW  JOINT  (ARTICULATIO  CUBITI) 

The  elbow  joint  is  of  the  ginglymus,  or  hinge  variety.  The  bones 
concerned  are  the  humerus,  ulna  and  radius.  The  humeroulnar 
articulation  comprises  the  trochlea  of  the  humerus  and  the  semilunar 
notch  of  the  ulna.  The  humeroradial  articulation  comprises  the 
capitulum  of  the  humerus  and  the  head  of  the  radius. 

The  capsule  surrounds  the  joint  and  is  made  up  of  individual 
ligaments  of  varying  thickness  that  join  so  as  to  make  a  complete 
investment  of  the  joint. 

The  ventral  ligament  (Jig.  anlerius)  consists  of  vertical,  oblique  and 
transverse  fibers.  It  is  attached,  proximally,  to  the  bone  just 
beyond  the  coronoid  and  radial  fossa?  of  the  humerus  and,  distally, 
to  the  margin  of  the  coronoid  process  of  the  ulna  and  the  annular 
ligament  of  the  radioulnar  articulation.  The  middle  portion  is  the 
strongest. 

The  thin  dorsal  ligament  (lig.  posterius)  is  attached,  proximally,  to 
the  margin  of  the  olecranon  fossa  and  capitulum  of  the  humerus  and, 


124 


>YNDESMOLOGY 


distally,  to  the  margins  and  tip  of  the  olecranon  process  of  the  ulna 
and  the  dorsal  aspect  of  the  radial  notch  of  the  ulna. 

The  ulnar  collateral  ligament  (lig.  collaterale  ulnare)  is  triangular 
and  fills  in  the  medial  part  of  the  capsule  between  the  two  preceding 
ligaments.  It  is  attached,  proximally,  to  the  edge  of  the  medial 
epicondyle  and,  distally,  to  the  medial  margin  of  the  semilunar 
notch  of  the  ulna.  Its  fibers  are  formed  into  three  bands  that  are 
called  ventral,  dorsal  and  transverse. 

A  synovial  membrane  lines  the  capsule  and  is  reflected  over  the 
nonarticular  portions  of  the  bones  within  the  joint  cavity.     Pads 


Internal 
epkondyL 


Articular  capsule 
Internal 
epicondyle 


Fig.  95-— The  left  elbow  joint  seen  from 
front.     'Sobotta  and  McMurrich.) 


Fig.  96. — The  left  elbow  joint  seer 
from  behind  and  from  the  radial  side 
{Sobotta  and  McMurrich.) 


of  fat  separate  it  from  the  capsule  in  the  coronoid  and  olecranno 
fossae. 

The  movements  of  the  elbow  joint  are  of  flexion  and  extension. 


RADIOULNAR  ARTICULATIONS 

There  are  two  radioulnar  articulations,  one  between  the  proximal 
extremities  of  the  two  bones  and  the  other  between  their  distal 
extremities.  They  both  represent  the  rotary,  or  lateral  ginglymus 
variety. 

The  proximal  radioulnar  articulation  (articulatio  radioulnaris 
proximalis)  consists  of  the  radial  notch  of  the  ulna  and  the  head  of  the 
radius. 


RADIOCARPAL    ARTICULATION 


The  annular  ligament  (lig.  annulare  radii)  holds  these  bones  in 
apposition.  It  is  attached  to  the  ventral  and  dorsal  margins  of  the 
radial  notch  and  is  obliquely  placed  so  as  to  form  a  funnel.  Its 
synovial  membrane  is  continuous  with  that  of  the  elbow  joint. 

The  distal  radioulnar  articulation 
{articulatio  radioulnaris  distalis) 
comprises  the  head  of  the  ulna  and 
the  ulnar  notch  of  the  radius.  The 
ventral  and  dorsal  radioulnar  ligaments 
are  transverse  bands  of  fibrous  tissue 
that  connect  the  adjoining  nonartic- 
ular  surfaces  of  the  bones.  A  dis- 
tinct capsular  ligament  does  not  exist. 

The  triangular  articular  disc  is 
important  in  binding  these  bones 
together.  Its  apex  is  attached  to 
the  depression  at  the  root  of  the 
styloid  process  of  the  ulna  and  its 
base  to  the  ridge  between  the  ulnar 
notch  and  the  distal  carpal  articular 
surface  of  the  radius. 

A  synovial  membrane  closes  the 
joint  cavity  and,  covering  the  ar- 
ticular surfaces  of  the  bones  extends 
proximally  between  the  ulna  and 
radius  as  the  recessus  sacciformis. 

Accessory  Ligaments. — The  oblique 
ligament  (chorda  obliqua)  is  an  ob- 
lique band  connecting  the  coronoid 
process  of  the  ulna  and  the  tuber- 
osity of  the  radius. 

The  interosseous  membrane  (mem- 
brana  interossea  anlebrachii)  is  a 
strong,  sheet-like  band  that  connects 
the  adjacent  margins  of  the  ulna  and 
radius,  distal  to  the  oblique  chord. 
Between  these  two  ligaments  there 
is  a  gap,  the  hiatus  interosseus. 

Movements  are  of  pronation   and 
supination. 
THE  RADIOCARPAL  ARTICULATION  (ARTICULATIO  RADIOCARPEA) 

The  radiocarpal  articulation  is  of  the  condyloid,  or  biaxial  variety. 
It  comprises  the  distal  extremity  of  the  radius,  the  discus  articularis, 
on  the  one  side,  and  the  scaphoid  (os  naviculare),  semilunar  (os 
lunatum),  and  cuneiform  (os  triquetrum)  bones,  on  the  other. 


Fig.  97. — The  bones  of  the  left  fore- 
arm with  the  interosseous  membrane; 
the  annular  ligament  has  been  divided. 
(Sobotta  and  McMurrich.) 


126  SYNDES1I0L0GY 

The  capsule  is  loose  and  its  thickened  portions  constitute  the 
following  ligaments. 

The  lateral  radiocarpal  ligament  (Jig.  radiocarpeum  laterale)  extends 
from  the  tip  of  the  styloid  process  of  the  radius  to  the  tuberosity  of 
the  navicular   bone. 

The  medial  ulnocarpal  ligament  (lig.  ulnocarpeum  mediale)  is  cord- 
like and  extends  from  the  styloid  process  of  the  ulna  to  the  triquetral 
and  pisiform   bones. 

The  ventral  radiocarpal  ligament  {lig.  radiocarpeum  volarc)  extends 
between  the  ventral  margin  of  the  distal  end  of  the  radius  and  the 
styloid  process  of  the  ulna  to  the  ventral  surfaces  of  the  navicular, 
lunate  and  triquetral  bones  and  sometimes  to  the  os  capitatum 
(magnum).  - 

The  dorsal  radiocarpal  ligament  [lig.  radiocarpeum  dorsale)  extends 
from  the  dorsal  margin  of  the  distal  end  of  the  radius  to  the  dorsal 
surfaces  of  the  first  row  of  carpal  bones. 

A  synovial  membrane  lines  the  joint. 

The  movements  are  of  flexion  and  extension,  abduction  and 
adduction. 

THE  CARPAL  ARTICULATIONS   tARTICDLATIONES  INTERCARPE^J 

The  carpal  articulations  are  all  of  the  arthrodial  variety. 

First  Row. — The  dorsal  ligaments  run  transversely  and  connect 
the  navicular  and  lunate  bones  and  the  lunate  and  triquetral  bones. 

The  ventral,  or  volar  ligaments,  are  thinner  but  and  similarly  placed. 

The  interosseous  ligaments  are  two  in  number,  one  connecting  the 
lunate  and  the  navicular  bones  and  the  other  the  lunate  and  tri- 
quetral bones.  These  are  at  the  proximal  ends  of  the  bones  and 
extend  from  ventral  to  dorsal  surfaces  and  shut  out  the  wrist  joint 
from  the  intercarpal  joints. 

The  pisiform  bone  has  three  ligaments.  The  capsule  connects  it 
with  the  triquetral  bone  and  it  has  its  own  synovial  membrane.  Its 
two  palmar  ligaments  connect  it  with  the  hamate  and  fifth  meta- 
carpal bones. 

Second  Row. — The  dorsal  ligaments  connect  the  great  multangular 
(trapezium)  with  the  lesser  multangular  (trapezoid),  the  latter  with 
the  os  capitatum  (magnum)  and  this  with  theoshamatum  (unciform). 

The  ventral,  or  volar  ligaments  are  similarly  arranged. 

The  interosseous  ligaments  are  three  in  number  and  connect  the 
bones  somewhat  as  in  the  first  row,  but  not  so  completely. 

The  articulation  between  the  first  and  second  rows  of  carpal  bones 
is  surrounded  by  a  short  capsular  ligament. 

The  ventral,  or  volar  ligament  (lig.  carpi  radiatum),  extends  between 
the  two  rows  on  their  ventral  surfaces. 

The  dorsal  ligament  is  thinner  but  similarly  arranged. 


THE    CARPAL   ARTICULATION 


127 


The  radial  collateral  carpal  ligament  extends  between  the  lateral 
surfaces  of  the  navicular  and  greater  multangular  bones. 

The  ulnar  collateral  ligament  extends  between  the  medial  surfaces 
of  the  triquetral  and  hamate  bones. 


Two  synovial  membranes  are  present,  one  between  the  pisiform 
and  triquetral  bones  (already  mentioned)  and  the  other  is  between 
the  two  rows  with  extensions  between  the  various  bones  forming  a 
labyrinthine  cavity. 

Movements. — Between  the  first  and  second  rows, flexion,  extension 
and  slight  rotation. 


1 28  SYNDESMOLOGY 

CARPOMETACARPAL    ARTICULATIONS 

The  articulation  of  the  first  (thumb)  metacarpal  with  the  great 
multangular  bone  is  one  of  reciprocal  reception.  It  permits  of  the 
greatest  movement  of  any  of  these  joints  and  a  loose  capsule 
surrounds  the  joint. 

Movements. — Flexion,  extension,  abduction,  adduction  and  circum- 
duction. 

The  articulations  between  the  other  metacarpal  and  carpal  bones 
are  of  the  arthrodial  variety. 

The  dorsal  ligaments  are  quite  distinct  and  extend  between  the 
dorsal  surfaces  of  the  bones  concerned. 

The  ventral,  or  volar  ligaments  are  similarly  arranged. 

Interosseous  ligaments  extend  between  the  capitate  and  hamate 
bones  and  the  adjacent  surfaces  of  the  third  and  fourth  metacarpal 
bones. 

The  synovial  membrane  is  continuous  with  that  between  the  first 
and  second  row  of  carpal  bones. 

Movements. — A  slight  gliding  movement,  only,  is  permitted. 

INTERMETACARPAL  ARTICULATIONS 

The  four  inner  metacarpal  bones  articulate  with  each  other  on 
their  adjacent  sides  (bases).  Dorsal  (ligg.  basalia  oss.  metacarp. 
dorsalia)  and  ventral  (ligg.  basalia  oss.  metacarp.  volaria)  ligaments 
connect  their  bases  transversely.  The  synovial  membranes  are  all 
extensions  of  and  continuous  with  that  between  the  two  rows  of 
metacarpal  bones. 

The  transverse  metacarpal  ligament  (lig.  capitulorum  oss.  mcta- 
carpalium  fpansversum)  is  a  strong  band  that  connects  the  heads  of 
the  four  inner  metacarpal  bones  (ventral  surfaces).  It  blends, 
distally,  with  the  metacarpophalangeal  ligaments  and,  proximally 
with  the  fascia  of  the  interosseous  muscles. 

THE  METACARPOPHALANGEAL  ARTICULATIONS 

These  joints  are  of  the  condyloid  variety. 

A  capsule  surrounds  each  joint  and  this  is  strengthened  dorsally 
by  the  expansions  of  the  tendons  of  the  m.  extensor  digitorum 
communis. 

The  ventral,  or  volar  ligament  (lig.  vaginale)  is  thick,  strong  and 
grooved  for  the  flexor  tendons. 

The  collateral  ligaments  (ligg.  collateral ia)  are  cord-like  thickenings 
of  the  lateral  parts  of  the  capsule. 

Movements. — Flexion,  extension  and  some  abduction,  adduction 
and  circumduction. 


TIIE    SACROILIAC    ARTICULATION" 


129 


ARTICULATIONS  OF  THE  PHALANGES  (ARTICULATIONES  DIGITORUM 

MANUSi 

These  joints  are  of  the  ginglymus  variety. 

A  capsule  is  present  and  is   strengthened   by  a  ventral,  or  volar, 
and  two  collateral  ligaments  arranged  similarly 
to  those  in  the  preceding  articulations. 

Each  of  these  joints  has  a  complete  sy- 
novial membrane  lining  the  joint  cavity. 

Movements. — Flexion  and  extension. 

THE  ARTICULATIONS  OF  THE  INFERIOR  EX- 
TREMITY (PELVIS  APPENDAGE) 

This  appendage  comprises  one-half  of  the 
pelvic  girdle  and  the  appendage  proper. 
The  pelvic  girdle  comprises  the  two  ossa 
coxae  (innominate  bones),  that  articulate 
with  each  other  ventrally  at  the  symphysis 
pubis,  and  with  the  sacrum  dorsally.  Upon 
each  side  the  girdle  articulates  with  the 
proximal  extremity  of  the  femur.  Accessory 
ligaments  are  also  present. 

THE    SACROILIAC    ARTICULATION    (ARTICU- 
LATIO   SACROLLIACA) 

This  articulation  is  of  the  amphiarthrodial 
variety.     A  joint  cavity  is  barely  preceptiblc. 

A  capsule  is  formed  by  the  following  ligament. 

The  ventral  sacroiliac  ligament  is  short,  thin  but  strong  and  extends 
between  the  ala  of  the  sacrum  and  the  iliac  fossa  of  the  hip  bone. 

The  dorsal  sacroiliac,  or  interosseous  ligament  extends  from  the 
supraauricular  area  of  the  ilium  to  the  tubercles  of  the  first  and 
second  sacral  segments  and  the  adjacent  bone.  There  are  two  parts, 
as  follows: 

The  short  dorsal  sacroiliac  ligament  extends  from  the  dorsal  superior 
spine  of  the  ilium  to  the  first  and  second  transverse  tubercles  of  the 
sacrum. 

The  long  dorsal  sacroiliac  ligament  extends  from  the  dorsal  superior 
spine  of  the  ilium  to  the  transverse  tubercles  of  the  third  and  fourth 
sacral  segments. 

Accessory  Ligaments. — The  sacrotuberous ,  or  great  sacrosciatic, 
ligament  (lig.  sacrotuberosum)  is  of  a  triangular  outline  but  narrow 
in  the  middle;  it  extends  from  the  dorsal  inferior  spine  of  the  ilium 
to  the  transverse  tubercles  and  the  lateral  margins  of  the  third, 
fourth  and  fifth  sacral  and  first  coccygeal  segments  and  to  the 
tuberosity  of  the  ischium,  inferior  to  the  groove  for  the  m.  obturator 
internus.  From  this  attachment  a  portion  passes  along  the  medial 
aspect  of  the  ramus  of  the  ischium  as  the  processus  falciformis. 


Fig.  100. — Articulations 
of  the  middle  finger  seen 
from  theside.  {Sobotta  and 
McMurrick.) 


13° 


SYNDESMOLOGV 


The  sacrospinous,  or  small  sacrosciatic  ligament  (lig.  sacrospinosum ) 
is  of  a  triangular  outline  and  lies  ventral  to  the  preceding  ligament. 
It  extends  from  the  last  two  sacral  and  the  first  coccygeal  segments 
to  the  spine  of  the  ischium. 

These  ligaments  convert  the  sciatic  notches  of  the  hip  bone  into 
foramina;  the  greater  foramen  (foramen  ischiadicum  majiis)  lies 
superior  to  the  sacrospinous  ligament  and  the  lesser  foramen  (foramen 
ischiudicum  minus)  lies  inferior  to  the  same  ligament. 


Lumbar  vertebra  l\ 
Anterior  sacro-iliae  lig. 


Anterior  longitudinal  ligament 
Iliolumbar  lig. 


Articular  capsule 
of  hip  joint 
Iliofemoral 


pubic  lig. 
Fig.  ioi. — The  male  pelvis  with  its  ligaments 


fibrocartilage  membrane 

front.     (Sobotta  and  McMurricli.) 


THE  SYMPHYSIS  PUBIS  (SYMPHYSIS  OSSIUM  PUBIS  j 


This  articulation  is  of  the  amphiarthrodial  variety  and  completes 
the  pelvic  girdle  ventrally. 

The  ventral  pubic  ligament  {lig.  pubicum  anterius)  is  short  and 
thick  and  extends  between  the  adjacent  surfaces  of  the  two  pubic 
bones.  Its  superficial  surface  is  strengthened  by  the  interlacement 
of  fibers  from  the  tendons  and  aponeuroses  of  the  adjacent  muscles. 

The  dorsal  pubic  ligament  {lig,  pubicum  poster  ins)  is  similarly 
arranged  but  weaker. 

The  superior  pubic  ligament  {lig.  pubicum  su  peri  us)  is  weak  and 
extends  from  one  pubic  crest  to  the  other. 

The  arcuate,  or  inferior  ligament  (lig.  arcualum  pubis),  is  quite 
strong  and  extends  from  the  descending  ramus  of  the  one  pubic 
bone  across  the  inferior  surface  of  the  joint  to  the  inferior  ramus 
of  the  other  pubic  bone. 


THE    HIP    JOINT 


131 


The  inter  pubic  disc  {lamina  fibrocartUaginea  inter  pubica)  is  covered 
with  hyalin  cartilage  and  is  attached  to  the  adjacent  surfaces  of  the 
two  pubic  bones.  It  may  contain  a  cleft-like  cavity  which,  however, 
does  not  contain  a  synovial  membrane. 

The  obturator  membrane  almost  completely  fills  in  the  obturator 
foramen  of  the  hip  bone.  At  its  highest  part  there  is  a  U-shaped 
gap  that  completes  the  obturator  canal. 


Short  post,  sacn-iliac  I 


WjS  Iliolumbar  ligament 

<^  ■/  5  ."'iliac  tig. 


■ 

;heroit$ 

■ 

Fig.   102. — The  female  pelvis 


from  behind.      (Sobotla  1 


THE  HIP  JOINT    ARTICULATIO  COXjE) 

The  hip  joint  is  of  the  enarthrodial  variety.  It  comprises  the  head 
of  the  femur  and  the  acetabular  cavity  of  the  hip  bone. 

The  labrum  glenoidale,  or  cotyloid  ligament  is  a  C-shaped  mass  of 
fibrocartilage  that  is  attached  to  the  rim  of  the  acetabular  cavity 
to  deepen  it  and  to  make  it  narrower.  The  gap  is  at  the  acetabular 
notch  and  here  the  two  ends  of  the  labrum  are  connected  by  the 
transverse  ligament  (lig.  transversantm  acetabuli).  This  ligament 
converts  the  notch  into  a  foramen  through  which  the  vessels  and 
nerves  pass  into  and  out  of  the  acetabular  cavity.  The  inner  surface 
of  the  labrum  is  articular. 

The  capsule  is  a  hollow  cylinder.  It  is  attached,  proximally,  to 
the  labrum  glenoidale  and  the  transverse  ligament  and  the  adjoin- 
ing bone;  distally,  it  is  attached,  above,  to  the  medial  aspect  of  the 


132 


SYNDESHOLOGY 


Pubocapsalar  ligament 


■ator  membrane 


Fig.    103. — The  right  hip  joint  seen  from  in  front.     (Sobotta  and  McMurrich.) 


FlG.  104. — The  right  hip  joint  seen  from  behind.     (Sobotta  and  McMurrich,) 


THE    HIP    JOINT  133 

greater  trochanter;  ventrally,  to  the  intertrochanteric  line;  dorsally, 
to  the  junction  of  the  middle  and  lateral  third  of  the  neck  and 
inferior]}-  to  the  region  of  the  lesser  trochanter.  Most  of  the  dorsal 
surface  of  the  neck  is  not  intrascapular  while  all  of  the  remainder  is. 

The  iliofemoral  ligament  (lig.  iliofemorale)  is  j^-shaped  and  sup- 
ports the  capsule  ventrally.  It  extends  between  the  inferior  margin 
of  the  superior  spine  of  the  ilium  to  the  intertrochanteric  line  of  the 
femur,  splitting  as  it  descends. 

The  pubocapsular  ligament  (lig.  pubocapsularis)  extends  from  the 
superior  ramus  of  the  pubis  and  obturator  crest  to  the  capsule,  with 
which  it  blends. 

The  ischiocapstilar  ligament  {lig.  ischiocapsularis)  consists  of  fibers 


Tendon  of 
rectus  femoris 

i 


Fossa  of  acetabulum 
Round  ligament  X 


ligament  of  acetabulum 


Fig.  105. — Socket  of  the  right  hip  joint  after  cutting  through  the  articular  capsule  and  the 
round  ligament.     The  head  of  the  femur  has  been  removed.     (Sobotla  and  McMurrich.) 

that  extend  from  the  region  of  the  lesser  sciatic  notch  to  the 
acetabular  portion  of  the  capsule  to  blend  therewith. 

The  round  ligament  (lig.  teres  femoris)  is  a  flattened  band  extend- 
ing from  the  superior  portion  of  the  depression  in  the  head  of  the 
femur  to  the  lower  margin  of  the  transverse  ligament  and  to  the 
adjacent  margins  of  the  acetabular  notch. 

The  fossa  in  the  acetabular  cavity  contains  a  mass  of  fat  that  is 
called  the  Haversian  gland.  This  is  covered  by  the  synovial  mem- 
brane so  that  it  lies  external  to  this  membrane. 

The  synovia!  membrane  lines  the  capsule  and  covers  all  parts  of 
the  bones  within  the  joint  except  the  actually  articulating  portions. 
Occasionally  a  bursa  is  found  communicating  with  the  ventral  part 
of  the  synovial  sac.     This  is  beneath  the  tendon  of  the  m.  iliopsoas. 

Movements. — This  joint  is  capable  of  flexion,  extension,  abduction, 
adduction,  rotation  and  circumduction. 


134 


SYNDESMOLOGY 
THE  KNEE  JOINT  (ARTICULATIO  GENU) 


The  knee  joint   is  the  largest  joint  in  the  body  and   is  of    the 
lynius  variety.     Three  bones,  the  femur,  tibia  and  patella  enter 
into  its  formation.     The  condyles  of  the  femur  articulate  ventrally 


Fig.  106. — The  right  knee  joint  in 
tension  seen  from  in  front.  (Sobotta 
McMurrich.) 


G.    107.— The  right  knee  joint  seen  f 
behind.      {Sobotta  and  McMurrich.) 


with  the  patella  and  distally  with  the  condylar  facets  upon  the  head 
of  the  tibia. 

The  capsule  in  itself  is  not  a  complete  investment  nor  are  the 
special  portions  sufficient  to  form  a  complete  capsule.  The  latter 
is  completed  and  strengthened  by  expansions  from  the  various 
tendons  about  it. 


THE    KNEE    JOINT 


135 


The  patellar  ligament  {lig.  patella;),  a. ventral  ligament,  connects 
the  apex  of  the  patella  with  the  tuberosity  of  the  tibia. 

The  dorsal  ligament  (lig.  posterius)  is  thin  laterally  and  thick 
medially.  It  extends  from  the  margins  of  the  femoral  condyles  and 
popliteal  surface  just  superior  to  the  intercondylic  notch  to  the 
dorsal  margin  of  the  head  of  the  tibia.  The  tendon  of  the  m. 
semimembranosus  contributes  the  oblique  popliteal  ligament  (lig. 
popliteum  obliquum). 

The  tibial  collateral  ligament   (lig.   collaterale  tibiale),  or  internal 


Patellar  surface 


Anterior 
ligament 
Anterior  capitular 


pi    w*» 

Tuberosity  0/  tibia 

ight  knee  joint  in  flexion  after  m 
lateral  ligaments.     {Sobolta  a 


moval  or'  the  articular  capsule  and  the 
,:J  McMurrich.) 


lateral  ligament,  is  short  and  strong,  extending  from  the  medial 
condyle  of  the  femur,  inferior  to  the  adductor  tubercle,  to  the 
medial  surface  of  the  head  of  the  tibia. 

The  fibular  collateral,  or  externa!  lateral  ligament  (lig.  collaterale 
libidare),  is  a  cord-like  band  extending  from  the  lateral  condyle  of 
the  femur  to  the  head  of  the  fibula,  ventral  to  the  styloid  process. 
It  is  split  by  the  tendon  of  the  m.  biceps  femoris. 

Within  the  joint  cavity  a  number  of  important  ligaments  will  be 
found. 

The  cruciate  ligaments  (lig.  crnciata  genu)  are  ventral  and  dorsal. 
The  ventral  one  (lig.  cruciatum  anterius)  extends  obliquely  (laterally 
and  dorsallv)  from  the  front  of  the  intercondylic  eminence  of  the 


136  SYNDESMOLOGY 

tibia  to  the  dorsal  part  of  the  lateral  condyle  and  the  intercondylic 
notch. 

The  dorsal  one  (lig.  cruciatum  posterius)  is  shorter  than  and  dorsal 
to  the  preceding.  It  extends  obliquely  (ventrally  and  medially) 
from  the  area  dorsal  to  the  intercondylic  eminence  of  the  tibia  to 
the  medial  condyle  near  the  ventral  end  of  the  intercondylic  notch. 

Two  fibrocartilagcs  deepen  the  facets  upon  the  head  of  the  tibia. 

The  medial  meniscus  (meniscus  medialis),  or  internal  semilunar 
cartilage,  is  C-shaped.  Its  ends,  or  cornua  are  attached  to  the  head 
of  the  tibia  in  front  of  and  behind  the  ventral  cruciate  ligament. 
Its  margin  is  attached  to  the  margin  of  the  head  of  the  tibia  by  the 
short  coronary  ligament. 

Transverse  ligament 
Anterior  crucial  Deep  infrapatellar  bursa 

Patellar  lig. 
Internal 


Posterior  crucial  lig. 


Fig.   109. — The  condyles  of  the  tibia  with  the  two  menisci  and  the  origins  of  the  crucial  liga- 
ments.     (Sobotta  and  McMitrrich.) 


The  lateral  meniscus  (meniscus  lateralis),  or  external  semilunar 
cartilage,  is  roughly  semilunar.  Its  cornua  are  attached  to  the 
superior  surface  of  the  head  of  the  tibia  but  are  farther  apart  than 
the  cornua  of  the  other  cartilage.  It  is  also  attached  to  the  margin 
of  the  head  of  the  tibia  by  a  coronary  ligament. 

The  transverse  ligament  (lig.  transversum  genu)  binds  the  ventral 
margins  of  the  menisci  together. 

The  synovial  membrane  lines  the  capsule,  covers  the  bones  within 
the  capsule  and  also  invests  the  intraarticular  ligaments.  Between 
it  and  the  patellar  ligament  is  the  infrapatellar  pad.  In  this  region 
the  synovial  membrane  forms  folds,  the  plica  synovialis  patellaris 
and  the  plicce  alares  (two).  Bursce  exist  in  relation  with  the  joint. 
The  prepatellar  bursa  lies  between  the  patella  and  the  skin.  The 
deep  infrapatellar  bursa  lies  between  the  ligamentum  patellar  and 
the  tuberosity  of  the  tibia.  The  suprapatellar  bursa  lies  between 
the  femur  and  the  tendon  of  the  m.  quadriceps  extensor.  The 
subcutaneous  tibial  bursa  lies  between  the  tuberosity  of  the  tibia  and 
the  skin. 


THE    TIBIOFIBULAR    ARTICULATIONS 


137 


Anterior  capitular  ligament 


Movements. — This  joint  permits  of  flexion  and  extension.  Under 
certain  conditions  a  slight  rotation  is  permitted. 

THE  TIBIOFIBULAR  ARTICULATIONS 

An  articulation  of  the  arthrodial  variety  exists  between  the  proximal 
extremities    and     another     between     the 
distal  extremities  of  the  tibia  and  hbula. 

The  proximal  tibiofibular  articulation 
is  the  smaller  and  less  important.  A 
capsule  surrounds  the  joint  and  this  is 
strengthened  by  additional  ligaments. 

The  ventral  ligament  of  the  head  of  the 
fibula  (lig.  capituli  fibula  anterius)  ex- 
tends between  the  head  of  the  fibula  and 
the  adjacent  part  of  the  lateral  tibial 
condyle. 

The  dorsal  ligament  of  the  head  of  the 
fibula  (lig.  capituli  fibidoz  posterius)  is 
similarly  placed  but  thinner. 

A  synovial  membrane  is  present  and 
may  connect  with  that  of  the  knee  joint. 

The  distal  tibiofibular  articulation,  a 
synchondrosis,  is  merely  a  lateral  support 
to  ankle  joint. 

The  ventral  ligament  of  the  lateral  mal- 
leolus, or  anterior  inferior  tibiofibular 
ligament,  extends  between  the  ventral 
surfaces  of  the  distal  end  of  the  tibia  and 
the  lateral  malleolus  of  the  fibula. 

The  dorsal  ligament  of  the  lateral  mal- 
leolus, or  posterior  inferior  tibiofibular 
ligament  is  similar  in  position. 

The  distal  ligament  of  the  lateral  mal- 
leolus, or  transverse  inferior  tibiofibular 
ligament  extends  from  the  dorsal  margin 
of  the  tibia  to  the  pit  on  the  dorsomedial 
portion  of  the  lateral  malleolus. 

The  interosseous  ligament  is  strong  and 
connects  the  adjacent  surfaces  of  the 
distal  extremities  of  the  tibia  and  fibula. 
It  is  continuous  superiorly  with  the  interosseous  membrane. 

The  interosseous  membrane,  like  that  of  the  forearm,  connects  the 
adjacent  margins  of  the  two  bones  and  separates  ventral  and 
dorsal  muscles.  Superiorly  there  is  a  gap  for  the  anterior  tibial 
vessels  and  inferiorly  another  opening  for  the  peroneal  vessels. 


FlC.  IIO. — The  right  tibia 
and  fibula  with  their  ]  igaments. 
(Sobotta  and  McMurrich.) 


138 


SYNDESMOLOGY 


The  synovial  membrane  of  the  joint  is  an  extension  of  that  of  the 
ankle  joint. 

THE  ANKLE  JOINT  (ARTICULATIO  TALOCRURALIS I 

The  ankle  joint,  or  tibiotarsal  articulation  is  of  the  ginglymus 
variety.  The  bones  concerned  are  the  tibia,  fibula  and  talus 
(astragalus). 

A  capsule  is  formed  by  the  various  ligaments  and  these  vary  in 

strength. 


Fig.   III. — The  ankle  joint  : 


from  behind.      (Sobolta  and  \Ii.\lu 


The  ventral  ligament  is  thin  and  connects  the  margin  of  the  head 
of  the  tibia  with  the  margin  of  the  head  of  the  talus. 

The  dorsal  ligament  is  very  strong  and  consists  of  three  parts. 
The  ventral  fasciculus  (lig.  talofibular e  anterius)  is  the  shortest  and 
connects  the  ventral  margin  of  the  lateral  malleolus  with  the  talus 
in  front  of  its  articular  surface.  The  medial  fasciculus  (lig.  calcaneo- 
fibulare)  is  cord-like  and  connects  the  tip  of  the  malleolus  with  the 
side  of  the  calcaneum.  The  dorsal  fasciculus  (lig.  talofibulare 
poslcrius)  is  the  strongest  and  is  transversely  placed.  It  extends 
from  the  fibular  fossa  of  the  malleolus  to  the  dorsal  surface  of  the 
talus. 

The  deltoid  ligament  (lig.  deltoideum) ,  or  medial  ligament,  is  tri- 
angular in  shape  and  the  strongest  ligament  of  the  ankle  joint.  It 
extends   from    the   medial   malleolus    to    the    navicular,    talal   and 


THE    INTKRTAKSAL    ARTICULATIONS 


139 


calcaneal  bones.  It  has  a  number  of  divisions,  as  anterior,  posterior 
and  deep  (all  talotibial)  and  tibionavicular  and  tibiocalcaneal. 

The  synovial  membrane  that  lines  the  capsule  and  invests  the  non- 
articular  portions  of  the  bones  within  the  joint  sends  an  extension 
into  the  inferior  tibiofibular  articulation.  Pads  of  fat  separate  it 
from  the  bones  at  the  front  and  back  of  the  joint. 

Movements. — These  are  of  flexion  and  extension. 

THE    INTERTARSAL   ARTICULATIONS    (ARTICULATIONES 
INTERTARSEiE) 

The  intertarsal  articulations  are  of  the  arthrodial  variety. 
The  talocalcaneal  joint  is  formed  by  the  talus  and  the  calcaneum. 
In  addition  to  a  capsule  there  are  the  anterior,  posterior,  lateral, 


Deltoid  ligament 
Tendon  of  tibialis  (inter 

Dorsal 
tarsometatarsal  lig. 


Tendon  of  tibialis 
Sustentaculum  tali 


Calcaneus 

Calcaneal  tendon 


(.Sobotta  and  McMurrich.) 


medial  and  interosseous  talocalcaneal  ligaments,  which  connect 
corresponding  areas  of  the  two  bones. 

The  talocalcaneonavicular  joint  is  formed  by  the  talus,  calcaneum 
and  naviculare.  It  is  at  the  summit  of  the  anteroposterior  arch  of 
the  foot.  The  most  important  ligament  is  the  plantar  calcaneona- 
vicular ligament  as  it  gives  support  to  the  arch  and  forms  part  of  the 
articulation.  It  blends  with  the  deltoid  ligament  of  the  ankle  joint. 
Other  ligaments  are,  the  calcaneonavicular  part  of  the  bifurcate  liga- 
ment and  the  posterior  talonavicular  ligament. 

The  calcaneocuboid  articulation  is  surrounded  by  a  capsule  which 
is  supported  by  other  ligaments  as,  the  medial  calcaneocuboid  (the 
calcaneocuboid  part  of  the  bifurcate  ligament),  dorsal,  lateral  and 
inferior  calcaneocuboid  ligaments. 


140 


SYNDESMOLOGY 


The  cuneonavicular  articulation  concerns  the  navicular  and  three 
cuneiform  bones.  In  addition  to  the  capsule  there  are  the  dorsal 
and   plantar  cuneonavicular  ligaments. 

The  intercuneiform  articulations  are  two  in  number,  the  middle 
bone  taking  part  in  both.  The  ligaments  are  the  dorsal  and  plantar 
intercuneiform  ligaments. 

The  cuneocuboid  articulation  is  between  the  cuboid  and  the  third 
cuneiform  bones.  The  ligaments  are  the  dorsal,  plantar  and  interos- 
seous cuneocuboid  ligaments. 


Anterior 

talo-fibidar 

% 


-The  ligaments  of  the  foot 


tmts  Upmaia  Transverse  capitular  tig. 

from  above  and  from  the  outer  side.      (Sobotta 


THE  TARSOMETATARSAL  ARTICULATIONS   (ARTICULATIONES  TAR- 
SOMETATARSEjE) 

These  joints  are  formed  by  the  cuboid  and  three  cuneiform  bones, 
proximal]}-,  and  the  bases  of  the  five  metatarsal  bones,  distally. 
There  are  three  joints  and  they  are  of  the  arthrodial  variety. 

The  medial  tarsometatarsal  articulation  comprises  the  internal 
cuneiform  bone  and  the  base  of  the  first  metatarsal  bone  (great  toe). 
The  ligaments  are  the  capsule,  and  dorsal  and  plantar  tarsometatarsal 
ligaments. 

The  intermediate  tarsometatarsal  joint  comprises  the  three 
cuneiform  bones  and  the  bases  of  the  second,  third  and  a  part  of  the 
fourth  metatarsal  bones.  The  ligaments  are  dorsal,  plantar  and 
interosseous. 

The  lateral  tarsometatarsal  articulation  involves  the  cuboid  and 


THE    IXTERUETATARSAL    ARTICULATIONS 


141 


the  bases  of  the  fourth  and  fifth  metatarsal  bones.  The  ligaments 
are  dorsal  and  plantar. 

Each  of  the  three  joints  has  a  separate  synovial  membrane. 

Movements. — The  intertarsal  and  tarsometatarsal  articulations 
permit  of  a  gliding  movement.  In  the  tarsus  inversion,  eversion  and 
a  slight  rotation  may  be  produced. 


Sesamoid  bone 


Tendon  of  peronaeus  longits 
Plantar  tarsometatarsal  ligts. 


14. — The  ligaments  of  the  foot  seen  from  the  plantar  surface. 
McMurrich.) 


THE  INTERMETATARSAL  ARTICULATIONS 


These  joints  comprise  the  adjacent  surfaces  of  the  outer  four 
metatarsal  bones  only.  The  ligaments  are  the  dorsal,  ventral  (plantar  | 
and  interosseous  ligaments  of  the  bases.  In  addition  transverse  meta- 
tarsal ligaments  bind  the  bases  on  their  plantar  surfaces.  The  syno- 
vial membrane  is  an  extension  of  the  preceding  joints. 


142  SYNDESMOLOGY 

THE  METATARSOPHALANGEAL  ARTICULATIONS 

These  joints  are  of  the  condyloid  variety.  They  resemble  those 
of  the  hand  and  each  is  provided  with  a  modified  capsule,  a  plantar 
(accessory)  and  two  lateral  (collateral)  ligaments.  The  dorsal  liga- 
ment is  supplied  by  the  expansion  of  the  extensor  tendon  as  it  passes 
over  the  joint. 

Movements. — Flexion,  extension,  abduction  and  adduction. 

THE  INTERPHALANGEAL  ARTICULATIONS   (ARTICULATIONES 
DIGITORUM  PEDIS) 

These  joints  also  resemble  those  of  the  hand.  The  capsule  is  thin. 
The  other  ligaments  are  the  plantar  (accessory)  and  two  lateral 
(collateral).  The  dorsal  ligament  is  supplied  by  the  extensor  tendon. 
Each  capsule  has  its  own  synovial  membrane. 

Movements. — These  are  of  fle-xion  and  extension. 


CHAPTER  III 
MYOLOGY 

Muscle  tissues  are  those  that  produce  the  various  movements  of 
the  different  parts  and  organs  of  the  body.  Myology  is  that  division 
of  Anatomy  that  treats  of  the  origin,  insertion  and  actions  of  the 
muscles.  There  are  three  varieties  of  muscle  tissue,  voluntary 
striated,   involuntary  nonstriated  and  involuntary  striated. 

Voluntary  striated,  or  skeletal  muscle  tissue  consists  of  units 
called  muscle  cells.  These  are  cylindrical  in  shape,  vary  in  length 
from  2.5  cm.  to  12  cm.  and  in  from  25^  to  80/u  in  diameter.  Each  cell 
or  fiber  shows  longitudinal  and  cross-striations.  Each  fiber  consists 
of  a  large  number  of  delicate  fibrillar,  or  sarcostyles,  imbedded  in  the 
homogeneous  sarcoplasm  and  is  surrounded  by  a  delicate  membrane 
called  the  sarcolenima.  The  fibrillar  are  composed  of  sarcous  sub- 
stance which  stains  deeply  while  the  sarcoplasm  stains  faintly, 
thereby  causing  the  longitudinal  striations.  Each  fibril  is  not  an 
uninterrupted  thread  but  consists  of  segments  (sarcous  elements)  of 
equal  length  and  separated  from  one  another  by  an  interval  filled 
in  with  sarcoplasm.  These  segments  are  all  at  the  same  level  at 
any  given  part  of  the  fiber  causing,  thus,  the  cross-striations  or 
alternating  dark  and  dim  discs.  In  special  preparations  the  dim 
discs  are  seen  to  be  crossed  by  a  fine  dark  line  called  the  membrane 
of  Kraiise,  or  Dobie's  line.  The  nuclei  are  numerous  and  are  located 
at  the  periphery  of  the  sarcous  substance  just  beneath  the 
sarcolenima. 

A  muscle  consists  of  a  collection  of  muscle  fibers  and  exhibits  a 
definite  structure.  Each  muscle  is  surrounded  by  a  sheath  of  white 
fibrous  tissue  called  the  epimysium.  From  this  septa  are  sent  in 
which  divide  the  muscle  into  large  secondary  bundles;  these  are 
further  subdivided  into  primary  bundles,  or  fasciculi  each  of  which 
is  surrounded  by  a  sheath  called  the  perimysium.  Incomplete 
septa  extend  into  the  primary  fasciculi  and  ultimately  give  rise 
to  a  delicate  meshwork  all  of  which  constitutes  the  endomysium; 
this  supports  the  muscle  fibers,  smaller  nerves  and  vessels. 

This  variety  of  muscle  is  found  as  the  skeletal,  and  external  ocular 
muscles,  in  the  tongue,  pharynx,  upper  part  of  the  esophagus,  anus, 
diaphragm,  larynx  and  external  ear. 

The  involuntary,  or  smooth  muscle  tissue,  consists  of  small 
spindle-shaped  cells.  Each  cell  measures  from  25//  to  200/^  in  length 
143 


144 


fff 


0      "■  ■  *  .' 


r/ 


—A 


D 

Fig.  115. — A,  Longitudinal  section  of  smooth  muscle  fibers,     a.  Muscle  fiber;  6,  nucleus; 

c,  fibrous  tissue  between  fibers.  B,  Cross-section  of  smooth  muscle  fibers,  a.  Perimysial 
connective  tissue;  b,  blood-vessel;  c,  nucleated  fiber;  d,  nonnucleated  fiber.  C,  Longitud- 
inal section  of  voluntary  muscle  fibers,     a,  Sarcotemma;  b,  nucleus;  c,  end  of  muscle  fiber; 

d,  dark  bands;  e,  intermediate  disc;/,  nucleus;  g,  lateral  disc.  D,  Diagrammatic  section  of 
cross  and  long  striations.  a.  Dark  disc;  b,  lateral  discs;  c,  intermediate  disc.  £,  Cross- 
section  of  voluntary  muscle,  a.  Perimysium;  b,  endomysium;  c,  nucleus  of  perimysium;  d, 
fibrillar;  e,  nucleus  of  muscle;  /,  sarcolemma.  F,  Longitudinal  section  of  cardiac  muscle 
fiber,  a.  Muscle  fiber;  6,  nucleus;  c,  branch.  G.  Cross-section  of  cardiac  muscle  fibers,  a. 
Perimysial  sheath;  b,  nucleus  of  sheath;  c,  muscle  fiber;  d,  nucleus;  e,  radial  plates  of  fibrillae. 
(Radasch,  Histology.) 


MUSCLE    TISSUE  145 

and  5M  to  7M  in  diameter;  each  fiber  contains  a  single,  long,  slender, 
centrally  placed  nucleus.  The  fibers  are  arranged  in  bundles  that 
form  layers  in  the  hollow  organs.  It  is  found  in  the  gastrointestinal 
tract,  trachea,  bronchial  tubes,  within  the  eyeball,  in  the  genitouri- 
nary system,  in  the  blood  vascular  and  lymph  vascular  systems  and 
the  capsules  of  some  organs. 

The  involuntary  striated,  or  cardiac  muscle  tissue,  is  found  in  the 
heart  only.  Each  cell  is  a  short,  stubby  cylinder  measuring  from 
25M  to  200ju  in  length  and  25/z  to  40^  in  diameter.  According  to 
some  the  heart  muscle  is  considered  a  syncytium.  Each  cell  has 
cross-  and  longitudinal  striations;  the  fibrillar  are  radially  arranged 
but  are  not  present  in  the  nuclear  area.  A  single,  broad,  oval 
nucleus  is  found  near  the  center  of  each  fiber.  The  cells  are  arranged 
in  bundles  that  do  not  form  muscle  masses  as  in  the  first  variety, 
nor  are  they  arranged  in  regular  layers  as  in  the  second  variety.  For 
their  general  arrangement  see  "The  Heart." 

A  muscle  has  two  points  of  attachment;  that  which  usually  acts 
as  the  fixed  point  (the  part  from  which  the  muscle  usually  acts)  is 
called  its  origin,  while  the  point  acted  upon  (moved)  is  called  the 
insertion.  Muscles  are  usually  attached  to  the  periosteum  of  the 
bone  (but  may  be  attached  to  the  bone  directly,  to  ligaments  or  to 
the  skin)  by  means  of  tendons,  or  aponeuroses.  The  main  mass  of 
the  muscle  (between  the  tendons)  constitutes  the  venter  or  belly. 

Movements  are  not  the  result  of  the  action  of  a  single  muscle  but  of  a 
variable  number.  While  one  (or  more)  muscle  is  concerned  directly 
with  the  action  produced  other  muscles  (fixation  muscles)  steady 
various  joints  during  the  action.  The  actions  of  muscles  are  of  im- 
portance in  the  displacement  of  fractured  bones  and  the  deformities 
in  dislocations. 

Muscles  are  often  named  from  their  action  (extensors,  flexors, 
pronators,  supinators);  number  of  heads  (biceps,  triceps);  points  of 
attachments  (sternomastoid,  sternohyoid);  shape  (deltoid,  trapezius, 
rhomboideus) ;  situation  (ulnaris,  radialis,  tibialis) ;  direction  (rectus, 
obliquus,  transversal  is) ;  course  (orbicular,  or  sphincter). 

The  fibers  of  the  muscles  are  arranged  in  various  ways.  When 
parallel,  or  nearly  so,  they  form  quadrilateral  and  fusiform  muscles. 
When  they  converge  toward  a  common  point,  they  form  triangular 
muscles  (temporalis).  When  arranged  obliquely  and  attached  to  one 
or  both  sides  of  the  tendon,  they  constitute  penniform  muscles.  On 
one  side  they  are  called  unipennate  (peronei);  on  both  sides,  they 
constitute  bipennate  muscles  (rectus  femoris);  when  the  tendinous 
bands  are  numerous  and  the  fibers  are  obliquely  attached,  the  result 
is  a  multipennate  muscle  (deltoid). 

More  or  less  directly  connected  with  the  muscles  are  the  fascia. 
The  superficial  fascia  {fascia  superficialis),  or  panniculus  adiposus 


146  MYOLOGY 

is  that  loose  areolar  tissue  just  beneath  the  skin  where  the  fat  is 
deposited.  It  supports  the  cutaneous  nerves  and  vessels  and  is  the 
one  affected  in  dropsical  conditions. 

The  deep  fascia  (fascia  profunda)  is  in  close  relation  with  the  bones, 
ligaments  and  muscles.  It  is  of  variable  thickness  in  the  various 
regions  of  the  body.  It  envelops  the  entire  extremities  and  sends  in 
septa,  the  intermuscular  fascia?,  that  separates  the  muscles  from  one 
another.  It  assists  in  strengthening  joints  and  as  aponeuroses 
affords  attachment  to  muscles. 

There  are  said  to  be  347  pairs  of  muscle  and  two  single  muscles 
in   the  body. 

THE  MUSCLES  OF  THE  HEAD 

The  muscles  of  the  head  comprise  those  of  the  scalp  and  auricular, 
nasal,  oral  and  orbital  regions  as  well  as  those  of  mastication. 

THE  MUSCLES  OF  THE  SCALP 

The  superficial  fascia  of  the  scalp  is  firm  and  dense  and  is  attached 
to  the  skin;  it  contains  the  superficial  vessels,  nerves  and  considerable 
fat. 

The  m.  epicranius  (occipitofrontalis)  consists  of  two  bellies  with 
an  intervening  tendon.  The  frontal  portion  [frontalis)  arises  from 
the  galea  aponeurotica  (epicranial  aponeurosis)  and  at  the  orbital 
arch  blends  with  the  mm.  orbicularis  oculi  and  corrugator  supercilii. 
The  occipital  portion  [occipitalis)  arises  from  the  lateral  two-thirds 
of  the  superior  nuchal  line  of  the  occipital  bone  and  terminates  in  the 
galea  aponeurotica.  The  galea  aponeurotica  is  a  broad  and  extensive 
mass  of  dense  fibrous  tissue  that  connects  the  two  bellies  together; 
it  is  attached  laterally  to  the  temporal  ridges  and  dorsally,  between 
the  dorsal  bellies,  to  the  middle  of  the  superior  nuchal  line. 

Actions. — The  frontal  portion  draws  the  scalp  forward  and  elevates 
the  skin  over  the  root  of  the  nose  and  the  eyebrows.  This  action  is 
increased  in  fright  and  terror.  The  occipital  portion  draws  the 
scalp  backward. 

Nerves. — Occipitalis. — Posterior  auricular  branch  of  the  facial 
nerve. 

Frontalis. — Temporal  branch  of  the  same  nerve. 

THE  EXTRINSIC  MUSCLES  OF  THE  EAR 

The  m.  auricularis  anterior,  the  smallest,  arises  from  the  temporal 
fascia  and  is  inserted  into  the  top  of  the  root  of  the  auricle. 

The  m.  auricularis  superior,  the  largest,  is  fan-shaped  and  arises 
from  the  temporal  fascia  and  is  inserted  into  the  top  of  the  auricle. 

The  m.  auricularis  posterior  arises  from  the  surface  of  the 
mastoid  process  and  is  inserted  into  the  cranial  surface  of  the  auricle. 


MUSCLES    OF    THE    NASAL    REGION 


147 


Actions. — Practically  functionless. 

Nerves. — Auricularis  anterior  and  superior. — Temporal  branch  of 
the  facial  nerve. — Auricularis  posterior. — Posterior  auricular  branch 
of  the  same  nerve 


Frontal, 
Orbicularis   oculi 

(Palpebrdl  portion) 

L16.  palpebrals  mediate 
Procerus  .      , . 
Nasaiis  s^&J 


Galea  aponeurotica 

Auricularis  superior 


Orbicularis   OCul't 
orbital  portion) 


Occipitalis 


Can  in  us 
Orbicularis  oris 


Transversus  ment 


Plalysma 


116. — The  superficial  layer  of  the  facial  muscles; 
neck  seen  from  the  side  and  slightly  from  in  front. 


domastoideus 


id  the  neighboring  muscles  of  the 
{Sohotta  and  McMurrich.) 


THE  NASAL  REGION 


The  m.  procerus,  or  pyramidalis  nasi,  arises  from  the  frontalis 
muscle  and  the  skin  of  the  glabella  and  is  inserted  into  the  membrane 
that  stretches  over  the  nose. 

The  m.  nasaiis,  or  compressor  naris,  arises  from  the  maxilla  above 
the  incisor  fossa  and  is  inserted  into  the  above  membrane. 

The  mm.  dilatatores  nasi  are  attached  to  the  margin  of  the  nostril, 
one  anterior  to  the  other. 

The  m.  depressor  alae  nasi  arises  from  the  upper  part  of  the  incisor 
fossa  of  the  maxilla;  it  divides,  one  part  being  inserted  into  the  ala 
and  the  other  into  the  septum  of  the  nose. 

The  caput  angulare,  or  levator  labii  superioris  et  alaeque  nasi, 
arises  from  the  root  of  the  frontal  process  of  the  maxilla  and  is 
inserted  into  the  ala  of  the  nose  and  joins  the  m.  orbicularis  oris. 

Actions. — The  procerus  wrinkles  the  skin  over  the  bridge  of  the 
nose.  The  caput  annulare  elevates  the  upper  lip  (disdain  and  con- 
tempt).    The  other  muscles  act  as  indicated  by  their  names. 

Nerves. — All  are  supplied  by  the  facial  nerve. 


148 


THE  ORAL  REGION 


The  m.  orbicularis  oris  is  a  sphincter  muscle  connected  with  the 
other  muscles  that  converge  at  the  mouth.  The  superior  part  is 
attached  to  the  nasal  septum  (nasolabial  band)  and  the  incisor 
fossa  (superior  incisive  fasciculus  which  is  continuous  with  the 
mm.  buccinator  and  caninus);  the  inferior  part  is  attached  to  the 
mandible  at  each  side  of  the  symphysis  (inferior  incisive  fasciculis 
which  is  continuous  with  the  mm.  buccinator  and  caninus) ;  laterally 
it  is  joined  by  the  buccinator,  the  elevators  and  depressors  of  the 
lower  lip  at  the  angle  of  the  mouth. 

The  m.  quadratus  labii  superioris  consists  of  the  three  following 
muscles: 

The  caput  infraorbitale,  or  levator  labii  superioris,  arises  from  the 
maxilla  just  above  the  infraorbital  foramen  and  joins  the  orbicularis 
oris  muscle. 


Fig.  117. — The  oral  musculature  seen  from  behind.  The  muscles,  together  with  the 
integument,  have  been  separated  from  the  bones,  and  the  mucous  membrane  covering  the 
muscles  has  been  removed.     (Scbotla  ami  McMitrrich.) 


The  caput  angulare  has  been  described  above. 

The  caput  zygomaticus,  or  zygomaticus  minor  arises  from  the 
zygomatic  bone  and  is  inserted  into  the  margin  of  the  orbicularis  oris 
muscle. 

The  m.  caninus,  or  levator  anguli  oris,  arises  from  the  canine  fossa 
of  the  maxilla  and  is  inserted  into  the  orbicularis  oris  and  the  skin  of 
the  angle  of  the  mouth. 

The  m.  zygomaticus  (major)  arises  from  the  zygomatic  arch  and  is 
inserted  into  the  skin  and  into  the  orbicularis  oris  muscle. 

The  m.  triangularis,  or  depressor  anguli  oris,  arises  from  the 
oblique  line  of  the  mandible  and  is  inserted  into  the  skin  and  the 
orbicularis  oris  muscle. 

The  m.  risorius  is  a  portion  of  the  platysma  muscle  arising  from 
the  fascia  over  the  parotid  gland;  it  is  inserted  into  the  skin  of  the 
angle  of  the  mouth. 

The  m.  quadratus  labii  inferioris,  or  depressor,  arises  from  the 


THE    MUSCLES    OF    THE    ORBITAL    REGION  I49 

mandible  close  to  the  triangularis;  it  is  inserted  into  the  skin  of  the 
lower  lip  and  into  the  orbicularis  oris. 

The  m.  mentalis,  or  levator  menti  arises  from  the  incisor  fossa  of 
the  mandible  and  is  inserted  into  the  skin  of  the  chin. 

The  m.  buccinator  forms  the  bulk  of  the  cheek.  It  arises  from  the 
pterygomandibular  raphe  and  the  alveolar  processes  of  the  mandible 
and  maxilla.  At  the  angle  of  the  mouth  its  fibers  blend  with  those 
of  the  muscles  there. 

Actions. — These  are  the  muscles  of  expression  and  by  their  actions 
produce  the  effect  of  emotions  upon  the  face.  The  m.  orbicularis 
oris  causes  the  lips  to  pout,  protrude  unevenly,  or  compresses  the 
lips  in  various  degrees.  The  mm.  quadratics  superioris  and  zygomati- 
cus  draw  the  lips  upward;  the  mm.  zygomalicus,  risorius,  buccinator 
and  triangularis  draw  the  angle  of  the  mouth  laterally;  the  mm. 
triangularis  and  quadratus  inferioris  draw  the  lips  downward.  The 
m.  buccinator  flattens  the  cheek  and  draws  the  angle  laterally  and 
the  in.  mentalis  protrudes  the  lower  lip. 

Nerve  Supply — All  are  supplied  by  the  facial  nerve. 

THE   ORBITAL   REGION 

The  external  muscles  include  three. 

The  m.  orbicularis  oculi  is  a  sphincter  muscle  of  the  eyelids.  Its 
orbital  portion  spreads  over  the  cheek,  temple  and  forehead  (pars 
orbital  is)  and  the  palpebral  portion  (pars  palpebral- is)  is  contained 
in  the  eyelid.  Medially  the  palpebral  portion  is  attacked  to  the 
medial  palpebral  ligament  and  the  borders  of  the  nasolacrimal 
groove. 

The  pars  lacrimalis,  or  tensor  tarsi,  is  a  portion  of  the  above  muscle 
that  lies  behind  the  lacrimal  sac  and  extend  from  the  nasolacrimal 
groove  to  the  tarsal  ligaments.     It  closes  the  eyelids. 

The  m.  corrugator  supercilii  arises  from  the  medial  portion  of  the 
superciliary  arch  and  blends  with  the  deep  fibers  of  the  orbicularis 
oculi.     It  throws  the  skin  of  the  forehead  into  vertical  folds. 

Nerve  Supply. — All  are  supplied  by  the  facial  nerve. 

Within  the  orbit  are  the  orbital  muscles,  the  fascia  bulbi  and  the 
eyeball,  vessels  and  nerves.  These  structures  are  embedded  in  the 
orbital  fat.  The  fascia  bulbi,  or  capsule  of  Tenon,  represents  a 
bursa  upon  which  the  eyeball  moves.  One  layer  is  attached  to  the 
posterior  surface  of  the  eyeball  while  the  other  is  applied  to  the 
adjacent  fat.  The  layers  are  continuous  at  the  conjunctival  region. 
This  fascia  is  pierced  by  the  optic  nerve  and  the  tendons  of  the 
ocular  muscles  upon  which  it  is  prolonged  in  the  form  of  sheathes. 

The  m.  levator  palpebrae  superioris  arises  from  the  upper  part 
of  the  optic  foramen  and  as  it  passes  forward  it  spreads  out  and  is 
inserted  into  the  lid,  mainly  into  the  superior  border  of  the  superior 


150  MYOLOGY 

tarsal  plate.  It  is  also  inserted  into  the  conjunctiva,  the  orbicularis 
oculi  and  skin  of  the  upper  lid. 

Action. — Elevates  the  upper  lid. 

Nerve  Supply. — Superior  division  of  the  oculomotor  nerve. 

The  mm.  recti  are  the  superior,  inferior,  lateral  and  medial,  and 
they  all  arise  from  a  ring  of  fibrous  tissue  that  surrounds  the  optic 
foramen.  The  superior,  medial  and  superior  head  of  the  lateral 
rectus  all  arise  from  the  upper  part  of  this  ring  while  the  inferior 
rectus  and  the  inferior  head  of  the  lateral  rectus  arise  from  the 
inferior  portion  of  this  ring.  The  medial  and  lateral  recti  are  in- 
serted into  the  transverse  plane  of  the  eyeball  about  8  mm.  behind 
the   corneoscleral   junction.     The   superior   and   inferior   recti   are 


18. — Muscles  of  the  right  orbit. 


inserted  a  little  medial  to  the  vertical  axis  of  the  eyeball  about  8 
mm.  behind  the  corneoscleral  junction. 

The  m.  obliquus  superior  arises  from  the  lateral  margin  of  the 
optic  foramen,  passes  obliquely  to  the  superomedial  part  of  the 
orbit  where  its  middle  tendon  passes  through  a  fibrous  pulley  that 
is  here  attached.  It  then  turns  laterally  and  passes  between  the 
superior  rectus  and  the  eyeball  to  be  inserted  into  the  sclera  at  the 
equator  of  the  eyeball  between  the  lateral  and  superior  recti  muscles. 

The  m.  obliquus  inferior  arises  from  the  anteromedial  part  of  the 
floor  of  the  orbit  at  the  margin  of  the  nasolacrimal  groove.  It 
passes  laterally  between  the  inferior  rectus  and  the  floor  of  the  orbit 
and  then  between  the  lateral  rectus  and  the  eyeball  to  be 
inserted  into  the  sclera  between  the  superior  and  lateral  recti 
muscles  but  at  a  more  posterior  level  than  the  superior  oblique. 

Actions. — The  medial  and  lateral  recti  muscles  move  the  eyeball 
medially  and  laterally  in  the  horizontal  plane.  The  superior  and 
inferior  recti  tend  to  move  the  eyeball  in  the  vertical  plane  but  their 


THE    MUSCLES   OF    MASTICATION  151 

insertion  and  oblique  direction  cause  them  to  produce  some  inward 
movement  as  well  as  some  rotation.  This  action  of  the  superior 
rectus  is  corrected  by  the  inferior  oblique  while  the  same  action  of 
the  inferior  oblique  is  corrected  by  the  superior  oblique  muscle. 
Diagonal  movements  are  produced  by  the  two  contiguous  recti 
muscles  acting  at  the  same  time.  The  oblique  muscles  acting  alone 
produce  movements  upon  the  anteroposterior  axis  of  the  eyeball. 

Nerve  Supply. — The  lateral  rectus  by  the  abducent  nerve. 

The  superior  oblique  by  the  trochlear  nerve. 

The  remainder  of  the  orbital  muscles  by  the  oculomotor  nerve. 

The  m.  orbitalis,  or  Mueller's  muscle  consists  of  smooth  muscle 
tissue  and  spans  the  inferior  orbital  fissure  and  infraorbital  groove. 

Action. — Probably  assists  in  protrusion  of  the  eyeball. 

Nerve  Supply. — Sympathetic  nerves. 

MUSCLES  OF  MASTICATION 

The  m.  temporalis  arises  as  a  fan-shaped  mass  from  the  temporal 
fossa  and  the  temporal  fascia.  It  is  inserted  into  the  coronoid  proc- 
ess and  the  anterior  margin  of  the  ramus  of  the  mandible. 

Action. — Closes  the  mouth,  protrudes  and  retracts  the  mandible. 

Nerve  Supply. — Mandibular  division  of  the  trigeminal  nerve. 

The  m.  masseter  arises  superficially  from  the  anterior  two-thirds 
of  the  inferior  margin  of  the  zygomatic  arch  and  deeply  from  the 
medial  surface  of  the  entire  zygomatic  arch;  it  is  inserted  into  the 
lateral  surface  of  the  coronoid  process,  ramus  and  angle  of  the 
mandible. 

Action. — Closes  the  mouth. 

Nerve  Supply. — Mandibular  division  of  the  trigeminal  nerve. 

The  m.  pterygoideus  externus  arises  from  the  infratemporal  sur- 
face of  the  greater  wing  of  the  sphenoid  bone  (superficial  head),  and 
from  the  lateral  surface  of  the  lateral  plate  of  the  pterygoid  process 
of  the  same  bone  (deep  head).  It  is  inserted  into  the  anterior  part  of 
the  neck  of  the  mandible  just  below  the  condyle  and  into  the  capsule 
of  the  joint  and  the  articular  disc. 

Action. — Protrusion  and  lateral  movements  of  the  mandible. 

Nerve  Supply. — Mandibular  division  of  the  trigeminal  nerve. 

The  m.  pterygoideus  internus  arises  from  the  medial  surface  of 
the  lateral  pterygoid  plate  and  from  the  tuberosity  of  the  maxilla; 
it  is  inserted  into  the  medial  surface  of  the  angle  and  ramus  of  the 
mandible  behind  the  mylohyoid  groove. 

Action. — Closes  the  mouth  and  assists  in  protrusion  and  lateral 
movements  of  the  mandible. 

Nerve  Supply. — Mandibular  division  of  the  trigeminal  nerve. 


'5- 


Galea  aponeuroses 


Temporalis 


Occipitalis 


ularis 


Trapezius 
Splenius  capitis 
Parotid  oland 
Sternocleidomastoideus 
Alasseter  x 


Fig.  no. — The  deepest  layer  of  the  facial  muscles  and  the  temporalis.  .  The  caninus,  the 
zygomatic  arch,  a  portion  of  the  zygomatic  bone  with  the  origin  of  the  masseter  and  the  tem- 
poral fascia?  have  been  removed.     (Sobotla  and  McMurrich.) 


Palatine  mucous^^ 


Hamulus  of 
pterygoid  p, 


lohuoideus  x 


^(Ant.  belly) 


Fig.   120. — The  two  pterygoidei  seen  from  the 
skull  has  been  divided  in  the  sagittal  pi. 
tongue  and  soft  palate  have  been  remo1 

K   indicates  that  the  structures  so  marked,  in  the  muscle  illustrations,  have 
been  cut. 


irface.     The  anterior  portion  of  the 
and  the  temporal  bone  in  an  oblique  plane;  the 
(Sobotta  and  McMurrich.) 


THE    CERVICAL   MUSCLES  1 53 

THE  MUSCLES  AND  FASCIA  OF  THE  NECK 

The  superficial  fascia  is  very  thin  and  invests  the  m.  platysma. 

The  m.  platysma  is  a  broad  thin  sheet  of  muscle  that  (irises  from 
the  pectoral  and  deltoid  fascia;  and  passes  obliquely  upward  and 
inward  over  the  neck;  some  of  its  fibers  are  inserted  into  the  mandible 
while  the  remainder  pass  onto  the  lower  part  of  the  face  to  be  inserted 
into  the  skin  and  to  blend  with  the  other  muscles  at  the  angle  of  the 
mouth. 

Action. — Wrinkles  the  skin  of  the  neck,  assists  in  depressing  the 
angles  of  the  mouth  arid  may  assist  in  depressing  the  mandible. 

Nerve  Supply. — Facial  nerve. 

The  deep  fascia  (fascia  colli)  surrounds  all  of  the  muscles  of  the 
neck,  forms  the  carotid  sheath  and  sends  in  septa  that  have  received 
special  names.  Dorsally  it  is  attached  to  the  ligamentum  nuchse 
and  as  it  passes  ventrally  it  splits  at  the  dorsal  margin  of  the  sterno- 
mastoid  muscle  to  envelop  it,  uniting  again  at  the  ventral  margin  of 
this  muscle  to  envelop  the  infrahyoid  muscles  and  then  passes  to 
the  midline  of  the  neck.  It  is  attached,  superiorly,  to  the  inferior 
nuchal  line  of  the  occipital  bone  and  the  entire  length  of  the  body  of 
the  mandible;  inferiorly,  it  is  attached  to  the  sternum,  the  clavicle, 
first  rib  and  to  the  acromial  process  of  the  scapula. 

The  prevertebral  fascia  (fascia  prevertebralis)  is  the  transverse 
septum  that  passes  in  front  of  the  vertebral  column  and  the  preverte- 
bral muscles.  The  pretracheal  fascia  is  a  septum  that  arches  across 
the  neck  ventral  to  the  trachea  and  thyroid  gland,  assisting  in  form- 
ing the  carotid  sheath  on  each  side.  These  two  septal  fasciae  form 
a  compartment  containing  the  larynx,  trachea,  thyroid  gland, 
esophagus  and  pharynx.  The  carotid  sheath  forms  a  tubular  com- 
partment that  encloses  the  carotid  artery,  the  jugular  vein,  the  vagal 
and  descendens  hypoglossi  nerves.  The  prevertebral  fascia  lies  dorsal 
to  the  parotid  gland  and  assists  in  forming  the  stylomandibu- 
lar, sphenomandibular  and  pterygomandibular  ligaments. 

The  m.  sternomastoideus  arises  from  the  ventral  surface  of  the 
manubrium  sterni  (sternal  head)  and  from  the  medial  third  of  the 
superior  surface  of  the  clavicle  (clavicular  head).  It  passes  supe- 
riorly and  dorsally  in  an  oblique  manner  to  be  inserted  into  the  lateral 
surface  of  the  mastoid  process  of  the  temporal  bone  and  the  superior 
nuchal  line  of  the  occipital  bone. 

Action. — Flexes  the  head  laterally  and  rotates  it  toward  the  opposite 
side  if  acting  alone.  Both  acting  flex  the  head  upon  the  neck  and 
assist  in  raising  the  clavicle  and  sternum  in  forced  inspiration. 

Nerve  Supply. — Accessory  nerve  and  a  branch  from  the  second 
cervical  nerve  through  the  cervical  plexus. 


154 


MYOLOGY 
INFRAHYOID  MUSCLES 


The  m.  omohyoideus  consists  of  two  bellies;  the  dorsal  one  arises 
from  the  superior  margin  of  the  scapula  and  the  transverse  scapular 
ligament  and  ends  in  a  tendon   that   continues  as  the  ventral  belly 


that  is  inserted  into  the  body  of  the  hyoid  bone  along  its  inferior 
margin.  The  muscle  has  an  oblique  direction  and  the  middle  tendon 
is  held  in  position  by  a  process  of  cervical  fascia  that  is  attached 
to  the  clavicle  and  first  rib. 

Action. — Depresses  hyoid  bone  (after  elevation)  and  draws  it  to 
one  side  and  backward  if  one  alone  is  acting. 


THE    SUPRAHYOID    MUSCLES  155 

Nerve  Supply. — Ansa  cervicalis  formed  by  the  first  three  cervical 
nerves. 

The  m.  sternohyoideus  is  narrow  and  arises  from  the  dorsal  surface 
of  the  manubrium  sterni,  the  first  costal  cartilage  and  the  adjacent 
part  of  the  clavicle.  It  is  inserted  into  the  inferior  margin  of  the 
body  of  the  hyoid  bone. 

Action. — Depressor  of  the  larynx  and  hyoid  bone  after  elevation  in 
deglutition. 

Nerve  Supply. — Ansa  cervicalis. 

The  m.  sternothyreoideus  arises  from  the  dorsal  surface  of  the 
manubrium  sterni  and  the  first  costal  cartilage  and  is  inserted  into 
the  oblique  line  of  the  thyreoid  cartilage  of  the  larynx. 

Action. — Depressor  of  the  larynx  and  hyoid  bone. 

Nerve  Supply. — Ansa  cervicalis. 

The  m.  thyreohyoideus,  apparently  a  continuation  of  the  preced- 
ing, arises  from  the  oblique  line  of  the  thyreoid  cartilage  and  is 
inserted  into  the  body  and  greater  cornu  of  the  hyoid  bone. 

Action. — Depressor  of  the  hyoid  bone  and  elevator  of  the  thyreoid 
cartilage. 

Nerve  Supply. — Ansa  cervicalis. 

SUPRAHYOID  MUSCLES 

The  m.  digastricus  consists  of  two  bellies,  the  dorsal  one  of  which 
arises  from  the  digastric  notch  of  the  mastoid  process.  This  is 
directed  toward  the  hyoid  bone  where  the  middle  tendon  is  held  in 
place  by  a  band  of  cervical  fascia.  The  ventral  belly  continues  from 
this  tendon  and  is  inserted  into  the  digastric  fossa  of  the  mandible 
(near  the  symphysis  on  the  medial  surface). 

Actions. — Elevator  of  the  hyoid  bone  and  the  ventral  belly  depresses 
the  mandible. 

-Xii-cc  Supply. — Ventral  belly  by  the  mylohyoid  branch  of  the 
inferior  alveolar  division  of  the  trigeminal  nerve;  dorsal  belly  by  the 
facial  nerve. 

The  m.  srylohyoideus  arises  from  the  dorsolateral  portion  of  the 
base  of  the  styloid  process  of  the  temporal  bone  and  is  inserted  into 
the  body  of  the  hyoid  bone  near  the  omohyoideus. 

Action. — -Elevator  of  the  hyoid  bone. 

Nerve  Supply. — Facial  nerve. 

The  m.  mylohyoideus  is  broad  and  extensive  forming  the  floor  of 
the  buccal  cavity.  It  arises  from  mylohyoid  ridge  of  the  mandible 
and  is  inserted  into  the  body  of  the  hyoid  bone  and  a  fibrous  median 
raphe  that  extends  from  the  hyoid  bone  toward  the  chin. 

Actions. — Elevates  the  hyoid  bone  and  depresses  the  mandible. 

Nerve  Supply. — Mylohyoid  branch  of  the  inferior  dental  nerve 
(trigeminal). 


156  MYOLOGY 

The  m.  geniohyoideus  arises  from  the  inferior  mental  spines  (me- 
dial surface  of  the  symphysis  menti)  and  is  inserted  into  the  ventral 
surface  of  the  body  of  the  hyoid  bone. 

Actions. — Elevates  the  hyoid  bone  and  depresses  the  mandible. 

Nerve  Supply. — First  and  second  cervical  nerves  through  the 
hypoglossal  nerve. 

LINGUAL  MUSCLES 

The  intrinsic  muscles  are  given  in  the  description  of  the  "Tongue" 
(page   288).     The  extrinsic  muscles  are  given  below. 

The  m.  genioglossus  is  a  fan-shaped  muscle  arising  from  the  supe- 
rior mental  spines;  its  inferior  fibers  are  inserted  into  the  body  of  the 
hyoid  bone  while  the  remainder  are  inserted  into  the  tongue  from  its 
tip  to  the  base. 

Body  of  tono'ue 
filiate  papilla   I     L  0„^tadinsl;s  i;n6uae  inferior 
Root  o/tono'-   /LXJ     Oral  mucous  membrane  X 

G/ossopalatir. 


Sty/o - 

pbaruno'eus 

w~    x      Cenioolossus 
Gen'tohuoideus 
*S<    '     '    !j'i  ''il  *5     ^       riyoolossus 
Greater  comu  of       Vfl;||'l'|    \M^~^Hyoid  bone  (body) 
"  * — -v — *    ^^Huothureoid  membrane 

Thureohuoideus 

Fig.  123. — The  superficial  layer  of  the  musculature  of  the  tongue  seen  from  the  right  side. 
The  mandible  has  been  divided  immediately  to  the  right  of  the  median  line.  (Sobotto- 
and  McMurrich.) 

Actions. — Elevates  the  hyoid  bone,  depresses  the  mandible  and 
assists  in  protracting,  retracting  and  depressing  the  tongue. 

Nerve  Supply. — Hypoglossal  nerve. 

The  m.  hyoglossus  arises  from  the  body  and  greater  cornu  of  the 
hyoid  bone  and  is  inserted  into  the  side  of  the  tongue. 

Actions. — Elevates  the  hyoid  bone  and  depresses  the  tongue. 

Nerve  Supply. — Hypoglossal  nerve. 

The  m.  styloglossus  arises  from  the  tip  of  the  styloid  process  and 
the  stylohyoid  ligament  and  is  inserted  into  the  side  and  inferior 
surface  of  the  tongue,  decussating  with  the  mm.  hyoglossus  and  the 
glossopalatinus. 

Actions. — Elevates  the  tongue  and  assists  in  retracting  the  tongue. 

Nerve  Supply. — Hypoglossal  nerve. 


MUSCLES  OF  THE  PHARYNX  AND  PALATE         157 

The  m.  glossopalatinus  arises  from  the  inferior  surface  of  the  soft 
palate  and  is  inserted  into  the  side  of  the  tongue  blending  with  the 
m.  styloglossus  and  intrinsic  muscles. 

Action. — Elevates  the  base  of  the  tongue. 

Nerve  Supply. — Accessory  nerve  through  the  pharyngeal  plexus. 

The  m.  chondroglossus  is  a  variable  muscle  and  when  present  it 
arises  from  the  lesser  cornu  of  the  hyoid  bone  and  blends  with  the 
intrinsic  muscles  of  the  tongue. 

Action. — Negligible. 

Nerve  Supply. — Hypoglossal  nerve. 

PHARYNGEAL  AND  PALATAL  MUSCLES 

The  m.  constrictor  pharyngeus  superior  is  thin  and  arises  from  the 
inferior  portion  of  the  dorsal  margin  of  the  medial  pterygoid  plate, 
from  the  pterygomandibular  ligament,  the  mylohyoid  line  and  the 
mucous  membrane  of  the  floor  of  the  mouth.  Its  fibers  radiate 
dorsally  and  are  inserted  into  the  pharyngeal  tubercle  of  the  occipital 
bone  and  the  median  raphe.  Its  inferior  portion  is  overlapped  by 
the  middle  constrictor. 

The  m.  constrictor  pharyngeus  medius  arises  from  the  stylohyoid 
ligament  and  both  cornua  of  the  hyoid  bone.  It  is  inserted  into  the 
dorsal  median  raphe.     It  is  overlapped  by  the  inferior  constrictor. 

The  m.  constrictor  pharyngeus  inferior  arises  from  the  oblique 
line  of  the  thyreoid  cartilage  and  cricoid  cartilage  and  is  inserted  into 
the  dorsal  median  raphe. 

Actions. — These  are  the  muscles  of  deglutition. 

Nerve  Supply. — Accessory  nerve  through  the  pharyngeal  plexus. 
The  inferior  receives  branches  from  the  vagal  nerve  in  addition. 

The  m.  stylopharyngeus  arises  from  the  root  of  the  styloid  process 
and  is  inserted  into  the  wall  of  the  pharynx  and  the  superior  and 
dorsal  margins  of  the  thyreoid  cartilage  of  the  larynx. 

Actions. — Elevates  and  draws  laterally  the  wall  of  the  pharynx. 

Nerve  Supply. — Glossopharyngeal  nerve. 

The  m.  pharyngopalatinus  arises  from  the  soft  palate  and  is 
■inserted  into  the  dorsal  margin  of  the  thyreoid  cartilage  near  the 
m.  stylopharyngeus. 

Action. — Draws  the  pharynx  over  the  bolus  of  food  in  deglutition. 

Nerve  Supply. — Accessory  through  the  pharyngeal  plexus. 

The  m.  salpingopharyngeus  is  a  small  muscle  that  arises  from  the 
inferior  part  of  the  auditory  (Eustachian)  tube  and  blends  with  the 
m.  pharyngopalatinus. 

The  m.  levator  veli  palatini  arises  from  the  inferior  part  of  the 
cartilaginous  auditory  tube  and  from  the  apex  of  the  petrous  portion 


of  the  temporal  bone.  It  is  inserted  into  the  aponeurosis  of  the 
soft  palate. 

Action. — Elevates  the  soft  palate. 

Nerve  Supply. — Accessory  nerve  through  the  pharyngeal  plexus. 

The  m.  tensor  veli  palatini  arises  from  the  cartilaginous  portion 
of  the  auditory  tube  and  from  the  scaphoid  fossa  of  the  pterygoid 
process  and  the  spine  of  the  sphenoid  bone.  It  is  inserted  into  the 
dorsal  margin  of  the  soft  palate  and  into  the  palatal  aponeurosis. 


pharynoobasilar 


Stylopharyndeus 


Stylohuotdeus 


Constrictor 
pharuno'is  medi 


pheryno'eal  raph 


pharuno'eal  o'/ands 
—  styloid  process 
V parotid  o'land 


Constrictor 
pharuno'is  superior 

Pteryo'oideus  internus 

Submaxillary  o'land 


Fig.  124. — The  constrictors  o-  the  pharynx  seen  from  behind.  The  posterior  part  of  the 
skull  has  been  removed.  *,  A  bundle  of  the  superior  constrictor  arising  from  the  base  of 
the  skull.      (Sobotta  and  McMurrich.) 


Action. — Renders  the  palate  tense. 

Nerve  Supply. — Trigeminal  nerve  through  the  otic  ganglion. 

The  m.  glossopalatinus  (see  lingual  muscles). 

The  m.  uvulae  is  really  a  pair  of  muscles  and  these  are  the  only 
intrinsic  muscles  of  the  palate.  Each  arises  from  the  posterior 
nasal  spine  and  palatal  aponeurosis  and  is  inserted  into  the  tissues 
of  the  uvula. 


LATERAL  AND  PREVERTEBRAL  CERVICAL  MUSCLES 


!59 


Action. — Elevates  the  uvula. 

Nerve  Supply. — Accessory  nerve  through  the  pharyngeal  plexus. 

THE    LATERAL    AND    PREVERTEBRAL    CERVICAL    MUSCLES 

The  m.  scalenus  anterior  arises  from  the  anterior  tubercles  of  the 
transverse  processes  of  the  third,  fourth,  fifth  and  sixth  cervical 


vertebra?.     It  is  inserted  into  the  scalene  tubercle  and  ridge  of  the 
first  rib. 

The  m.  scalenus  medius  arises  from  the  posterior  tubercles  of  the 


l6o  MYOLOGY 

transverse   processes  of   the   inferior  six   cervical  vertebra  and  is 
inserted  into  the  first  rib  dorsal  to  the  subclavian  groove. 

The  m.  scalenus  posterior  arises  from  the  posterior  tubercles  of 
the  transverse  processes  of  the  fourth,  fifth  and  sixth  ribs  and  is 
inserted  into  the  lateral  surface  of  the  second  rib. 

Actions. — Lateral  flexion  of  the  vertebral  column  and  accessory 
to  respiration. 

Nerve  Supply. — Ventral  rami  of   the  lowest  four  cervical  nerves. 

The  m.  longus  capitis,  or  rectus  capitis  anticus  major  arises  from 
the  anterior  tubercles  of  the  transverse  processes  of  the  third,  fourth, 
fifth  and  sixth  cervical  vertebrae  and  is  inserted  into  the  basilar 
portion  of  the  occipital  bone. 

Action. — Flexes  the  head  and  the  cervical  vertebrae. 

Nerve  Supply. — Ventral  rami  of  the  first  four  cervical  nerves. 

The  m.  rectus  capitis  anterior,  or  rectus  capitis  anterior  minor 
arises  from  the  lateral  mass  of  the  atlas  and  is  inserted  into  the 
basilar  portion  of  the  occipital  bone. 

Action. — Flexes  the  head  upon  the  vertebral  column. 

Nerve  Supply. — From  the  loop  between  the  first  and  second 
cervical  nerves. 

The  m.  longus  colli  is  divisible  into  three  portions.  The  vertical 
part  arises  from  the  bodies  of  the  last  three  cervical  and  the  first 
three  thoracic  vertebrae  and  is  inserted  into  the  bodies  of  the  second, 
third  and  fourth  cervical  vertebrae.  The  superior  oblique  part 
arises  from  the  anterior  tubercles  of  the  third,  fourth  and  fifth 
cervical  vertebrae  and  is  inserted  into  the  anterior  tubercle  of  the 
atlas.  The  inferior  oblique  portion  arises  from  the  bodies  of  the 
first  three  thoracic  vertebrae  and  is  inserted  into  the  anterior  tubercles 
of  the  fifth  and  sixth  cervical  vertebrae. 

Action. — Flexes  the  vertebral  column. 

Nerve  Supply. — Ventral  rami  of '  the  second,  third  and  fourth 
cervical  nerves. 

The  m.  rectus  capitis  lateralis  arises  from  the  transverse  process 
of  the  atlas  and  is  inserted  into  the  jugular  process  of  the  occipital 
bone. 

Action. — Flexes  the  head  laterally  upon  the  vertebral  column. 

Nerve  Supply. — The  loop  between  the  first  and  second  cervical 
nerves. 

MUSCLES  OF  THE  BACK 

The  superficial  fascia  is  thin  and  contains  a  variable  quantity 
of  fat.  The  deep  fascia  is  usually  more  prominent.  It  is  attached, 
superiorly,  to  the  superior  nuchal  line  of  the  occipital  bone  and  is 
continuous  with  the  cervical  fascia.  It  is  continuous  with  the 
axillary  fascia  and  the  fascia  of  the  abdomen  and  thus  covers  the 


THE    MUSCLES    OF    THE   BACK 


161 


superficial  muscles  and  even  ensheathes  them.  In  the  middorsal 
line  it  is  attached  to  the  ligamentum  nuchas  and  the  vertebral 
spines;  it  is  also  attached  to  the  spine  of  the  scapula  and  to  the  crest 
of  the  ilium.  The  muscles  are  superficial  and  deep  and  are  usually 
described  under  four  layers. 

The  mm.  trapezius  and  the  latissimus  dorsi  form  the  superficial 
layer. 

The  m.  trapezius  is  broad,  thin,  flat  and  of  a  triangular  form.  It 
arises  from  the  medial  portion  of  the  superior  nuchal  line  of  the 


Semispinal''^  capit 

Splenius  capitis 


Sternocleidomastoideus 


Sacrospinalis 


fc      I  posterior  layer) 


Gluteal  fascia 


Fig.  i  2- . — The  superficial  layer  of  the  flat  muscles  of  the  back  together  with  the  neighbor- 
ing muscles  of  the  head,  neck,  abdomen,  and  buttock.  Upon  the  right  side  the  rhomboideus 
major  and  the  teres  major  are  represented  covered  by  fascia.     (Sobotta  and  McMurrich.) 

occipital  bone,  from  the  ligamentum  nucha;  and  from  the  spines  of 
the  seventh  cervical  and  all  of  the  thoracic  vertebrae  as  well  as  the 
supraspinous  ligaments.  The  superior  fibers  are  inserted  into  lateral 
third  of  the  dorsal  margin  of  the  clavicle;  the  middle  fibers  are  inserted 
into  the  medial  margin  of  the  acromion  and  the  superior  margin 
of  the  spine  of  the  scapula;  the  inferior fibers  are  inserted  into  the  base 
of  the  spine  of  the  scapula. 


I 62  MYOLOGY 

Action. — The  whole  muscle  rotates  the  scapula.  The  superior 
portion  elevates  the  shoulder  girdle  while  the  inferior  fibers  depress 
the  vertebral  margin. 

Nerve  Supply. — The  accessory  nerve  and  the  third  and  fourth 
cervical  nerves  through  the  cervical  plexus. 

The  m.  latissimus  dorsi  is  also  a  flat,  triangular  muscle.  It 
arises  from  the  lumbosacral  fascia,  from  the  lower  three  or  four  ribs 
(interdigitating  with  the  m.  obliquus  abdominis  externus)  and  occa- 
sionally from  the  inferior  angle  of  the  scapula.  Toward  its  inser- 
tion the  muscle  becomes  narrow  and  thick  and  its  ribbon-like  tendon 
is  inserted  into  the  floor  of  the  intertubercular  sulcus  (bicipital 
groove). 

Action. — Depresses  and  rotates  the  humerus  medially  and  as  a 
muscle  of  extraordinary  inspiration  it  elevates  the  inferior  ribs. 

Nerve  Supply. — The  thoracodorsal  nerve  from  the  dorsal  cord  of 
the  brachial  plexus  (representing  sixth,  seventh  and  eighth  cervical 
nerves). 

SECOND  LAYER 

The  m.  levator  scapula  is  a  narrow  muscle  that  arises  from  pos- 
terior tubercles  of  the  transverse  processes  of  the  first  three  or  four 
cervical  vertebra  and  is  inserted  into  the  superior  angle  and  vertebral 
margin  of  the  scapula. 

Action. — Elevates  the  superior  angle  and  vertebral  margin  of  the 
scapula. 

Nerve  Supply. — Dorsal  scapular  nerve  of  the  brachial  plexus  (fifth 
cer.)  and  branches  from  the  third  and  fourth  cervical  nerves. 

The  m.  rhomboideus  minor  arises  from  the  ligamentum  nucha? 
and  the  spines  of  the  seventh  cervical  and  first  thoracic  vertebra?. 
It  is  inserted  into  vertebral  margin  of  the  scapula  at  the  base  of  the 
spine. 

The  m.  rhomboideus  major  arises  from  the  spines  of  the  second, 
third,  fourth  and  fifth  thoracic  vertebra;  and  supraspinous  ligaments. 
It  is  inserted  into  the  vertebral  margin  of  the  scapula  at  the  base  of 
the  spine  and  at  the  inferior  angle. 

Actions. — They  elevate  and  draw  toward  the  median  line  the 
vertebral  margin  of  the  scapula. 

Nerve  Supply. — Dorsal  scapular  nerve  of  the  brachial  plexus 
(fifth  cer.). 

THIRD  LAYER 

The  m.  serratus  posticus  superior  arises  from  the  ligamentum 
nuchas  and  the  spines  of  the  seventh  cervical  and  first  three  thoracic 
vertebra;.  It  is  inserted  into  the  second,  third,  fourth  and  fifth 
ribs. 

The  m.   serratus  posticus  inferior  arises  from  the  lumbosacral 


THE  MUSCLES  OF  THE  BACK 


163 


fascia  attached  to  the  last  two  thoracic  and  first  two  lumbar  spines; 
after  a  horizontal  course  it  is  inserted  into  the  last  four  ribs. 

Actions. — Extensors  of  the  vertebral  column  and  accessory  muscles 
of  respiration. 

Nerve  Supply. — Dorsal  rami  of  the  superior  and  inferior  thoracic 
nerves,  respectively. 

The  m.  splenius  is  a  band-like  muscle  that  arises  from  the  lig. 
nuchae,  the  last  cervical  and  the  first  six  thoracic  spines  and  the 


Splenius  capitis 
Levator  scapulae 
Rhomboideus  minor 
tSupraspinatus) 


Rhomboideus 
major 


Occipitalis 
Semispinalis  capitis 
Sternocleidomastoideus 
Splenius  cervicis 
Levator  scapulae 
^Trapezius  y 


Latissimus  X 


Latissimus  x 

Serratus 

§;'.\  posterior  inferior 

.umbodorsal  fascia 
I  posterior  layer) 

Gluteal  fascia 


(Glutaeus  maximus) 


Fig.   1  28. — The  deeper  layers  of  the  flat  muscles  of  the  back.      On  the  left  side  the  trape- 
zius and  latissimus  have  been  cut  away;  on  the  right  side  the  rhomboidei  have  also  been  cut 
'    1  and  the  lumbodorsal  fascia  has  been  retained  only  where  it  is  in  relation  with 
the  origin  of  the  serratus  posterior  inferior  and  below.      (Sobolla  and  Ml  Murrich.) 


supraspinous  ligaments.  The  superior  portion  is  inserted,  as  the 
splenius  capitis  into  the  mastoid  process  and  the  superior  nuchal  line. 
The  inferior  portion,  as  the  splenius  cervicis,  is  inserted  into  dorsal 
tubercles  of  the  first  three  or  four  cervical  vertebra?. 

Actions. — Extension  and  lateral  movement  of  the  vertebral  column. 
The  splenius  capitis  assists  in  flexion,  rotation  and  raising  the  head. 


1 64 


MYOLOGY 


Nerve  Supply. — Dorsal  rami  of  the  cervical  and  superior  thoracic 
nerves. 

FOURTH  LAYER 

The  m.  sacrospinalis,  or  erector  spinse,  is  the  large  muscle  mass 
that  tills  the  vertebral  groove  on  each  side  of  the  spinous  processes. 
It  arises  from  the  iliac  crest,  from  the  dorsal  sacral  ligament  and 
from  the  dorsum  of  the  sacrum  and  the  spinous  processes  of  the 


Iliocostalis 
turn  bo  rum 


FlG.   129. — The  deeper  layers  of  the  lo 
spinalis  has  been  partly  removed  and  the  i 
anil  McMurrich.) 


'spinalis  capitis  X 

Rectus  capitis 
major 


Splenius  capitis  X 
ObUquus 
capitis  super. 

longissimus  capitis  X 
Obliquus  capitis  inferior 
Spinalis  cervicis 
Semispinalis  capitis  X 
fnterspinales 
~  5  err  at  us 
poster,  super,  X 

Semispinalis  ceroids 
et  dorsi  X 


Multifidus  dorsi 


Legator  costae 

Levator  costae 

fono'us 


5 er rat us 
posterior  inf 


Semispinalis  X 


:he  back.     On  the  left  side 
pinalis  has  been  cut  and  reflected. 


lumbar  and  superior  sacral  vertebrae.  Near  the  last  rib  the  muscle 
divides  into  several  portions,  as  follows: 

The  m.  iliocostalis  lumborum,  or  lateral  portion,  is  inserted  into  the 
six  inferior  ribs. 

The  m.  iliocostalis  dorsi,  or  accessorius,  is  the  successor  of  the 
preceding  in  the  upper  thoracic  region.  It  arises  from  the  inferior 
six  ribs,  medial  to  the  iliocostalis  lumborum  and  is  inserted  into  the 
six  superior  ribs. 


THE  MUSCLES  OF  THE  BACK  165 

The  m.  iliocostalis  cervicis,  or  cervicis  ascendens,  succeeds  the 
m.  iliocostalis  dorsi  in  the  cervical  region.  It  arises  from  the 
superior  six  ribs  medial  to  the  insertion  of  the  preceding  muscle  and 
is  inserted  into  the  dorsal  tubercles  of  the  fourth,  fifth  and  sixth 
cervical  vertebra?. 

The  m.  longisimus  is  the  medial  and  largest  portion  of  the  m. 
sacrospinalis.  It  is  inserted  into  all  of  the  ribs  and  into  the  trans- 
verse processes  of  the  thoracic  and  lumbar  vertebra?. 

The  m.  longisimus  cervicis,  or  transversalis  cervicis,  arises  from 
the  transverse  processes  of  the  first  six  thoracic  vertebra?  and  is 
inserted  into  the  dorsal  tubercles  of  the  transverse  processes  of  the 
third,  fourth,  fifth  and  sixth  cervical  vertebra?. 

The  m.  longisimus  capitis,  or  trachelomastoideus,  arises  in  com- 
mon with  the  preceding  and  from  the  articular  processes  of  the  lower 
four  cervical  vertebra?.  It  is  inserted  into  mastoid  process  of  the 
temporal  bone. 

The  m.  spinalis  dorsi  lies  just  lateral  to  the  midline  in  the  thoracic 
region.  It  arises  from  the  spinous  processes  of  the  first  two  lumbar 
and  the  last  two  thoracic  vertebra?  and  is  inserted  into  the  spines  of 
the  first  four,  or  more,  thoracic  vertebra?. 

The  m.  semispinalis  capitis,  or  complexus,  is  a  broad  muscle  that 
arises  from  the  transverse  processes  of  the  first  six  thoracic  and  the 
articular  processes  of  the  last  four  cervical  vertebra?.  It  is  inserted 
into  the  occipital  bone  between  the  superior  and  inferior  nuchal  lines. 

Actions. — Assists  in  extension  and  lateral  movements  of  the  pelvis 
and  vertebral  column.  Extension,  lateral  movement  and  rotation 
of  the  head  (mm.  long,  capitis  and  semispinalis  capitis).  Accessory 
to  inspiration  (mm.  longisimus  and  iliocostales). 

Nerve  Supply. — Dorsal  rami  of  the  spinal  nerves. 

FIFTH  LAYER 

The  m.  semispinalis  comprises  two  portions. 

The  m.  semispinalis  dorsi  arises  from  the  transverse  processes  of 
the  last  six  thoracic  vertebra?  and  is  inserted  into  the  spines  of  the 
first  four  thoracic  and  last  two  cervical  vertebra?. 

The  m.  semispinalis  cervicis,  or  colli,  arises  from  the  transverse 
processes  of  the  first  six  thoracic  and  the  articular  processes  of  the  last 
four  cervical  vertebra?  and  is  inserted  into  the  spines  of  the  second  to 
the  fifth  cervical  vertebra?. 

Actions. — Extension,  rotation  and  lateral  movement  of  the  vertebral 
column. 

Nerve  Supply. — Dorsal  rami  of  the  spinal  nerves. 

The  m.  rotatores  are  eleven  pairs  of  small,  thoracic  muscles.  Each 
arises  from  the  transverse  process  and  is  inserted  into  the  lamina  of 
the  vertebra  superior  to  it. 


l66  MYOLOGY 

Action. — Extension  and  rotation  of  the  vertebral  column. 

Nerve  Supply. — Dorsal  rami  of  the  thoracic  spinal  nerves. 

The  mm.  interspinals  are  paired  muscles  connecting  the  trans- 
verse processes  of  the  vertebrae.  They  extend  the  vertebral  column 
and  are  supplied  by  the  dorsal  rami  of  the  spinal  nerves. 

The  mm.  intertransversarii,  or  intertransversales,  are  small  mus- 
cles connecting  the  adjacent  transverse  processes.  In  the  neck  and 
lumbar  region  they  are  paired  on  each  side  of  the  midline.  These 
assist  in  lateral  movement  and  rotation  of  the  vertebral  column  and 
are  supplied  by  the  ventral  rami  of  the  spinal  nerves. 

The  m.  rectus  capitis  posterior  major  arises  from  the  spine  of  the 
second  cervical  vertebra  and  is  inserted  into  the  occipital  bone  below 
the  middle  of  the  inferior  nuchal  line. 

The  m.  rectus  capitis  posterior  minor  arises  from  the  dorsal  tu- 
bercle of  the  atlas  and  is  inserted  into  the  occipital  bone  medial  to  the 
preceding  muscle. 

Actions. — Both  muscles  assist  in  elevation,  rotation  and  lateral 
movement  of  the  head. 

Nerve  Supply. — Dorsal  ramus  of  the  suboccipital,  or  first  cervical, 
nerve. 

The  m.  obliquus  capitis  superior  arises  from  the  transverse  process 
of  the  atlas  and  is  inserted  into  the  lateral  portion  of  the  occipital  bone 
between  the  superior  nuchal  line  and  the  jugular  process. 

The  m.  obliquus  inferior  arises  from  the  spine  of  the  epistropheus 
(axis)  and  is  inserted  into  the  transverse  process  of  the  atlas. 

Actions. — The  superior  produces  elevation,  rotation  and  lateral 
movement  of  the  head  upon  the  atlas.  The  inferior  produces  extens  ion , 
lateral  movement  and  rotation  of  the  atlas  in  the  axis. 

Nerve  Supply. — Posterior  ramus  of  the  suboccipital  or  first  cervical 
nerve. 

The  m.  rectus  capitis  lateralis  connects  the  jugular  process  of  the 
occipital  bone  with  the  transverse  process  of  the  atlas.  It  assists  in 
lateral  movement  and  rotation  of  the  head  and  is  supplied  by  the  sub- 
occipital nerve. 

MUSCLES    OF   THE   THORAX,    OF   RESPIRATION 

The  mm.  intercostales  are  placed  between  the  ribs  and  are  eleven 
pairs  in  number  on  each  side. 

Each  external  intercostal  muscle  (m.  intcrcostalis  externus)  arises 
from  the  inferior  margin  of  a  rib,  passes  downward  and  ventrally  to 
be  inserted  into  the  superior  margin  of  the  rib  beneath.  It  does  not 
quite  reach  the  sternum  in  front  and  the  space  is  spanned  by  the 
ventral  intercostal  aponeurosis. 

Each  internal  intercostal  muscle  (m.  intercostalis  interims)  arises 
from  the  costal  cartilage  and  the  medial  margin  of  the  costal  groove 


THE    DIAPHRAGM 


167 


and  passes  downward  and  dorsally  to  be  inserted  into  the  superior 
margin  of  the  costal  cartilage  and  rib  beneath.  It  extends  to  the 
angle  of  the  rib  only  and  the  remainder  of  the  intercostal  space  is 
spanned  by  the  dorsal  intercostal  aponeurosis. 

The  mm.  levatores  costarum  are  twelve  in  number  arising  from 
the  transverse  processes  of  the  seventh  cervical  and  the  first  eleven 
thoracic  vertebrae;  each  is  inserted  into  the  rib  dorsal  to  the  angle. 

The  mm.  subcostales  are  on  the  medial  surfaces  of  the  inferior  ribs 
near  their  angles.  These  are  in  series  with  the  internal  intercostal 
muscles. 


Anterior  fanaitudinal  //'{foment 

Intercostales  extern? 


SUrnothyreoide!  X 


Rib  XI 


RibXIl   Lumbar  vertebra  I  Subcostales 
Fig.    131. 
lavicles  and  the  ribs,  with  the  intercostales. 


Fig.  130. 

Fig.   130. — The  sternum,  sternal  ends  of  the 
and  the  transversus  thoracis,  seen  from  behind.     (Sobotta  and  McMurrich.) 

Fig.  131, — The  fifth  to  the  twelfth  thoracic  vertebra:  and  the  vertebral  extremities  of  the 
corresponding  ribs,  with  the  intercostales  and  subcostales  seen  from  in  front.  On  the  left  side 
the  intercostal  ligaments  have  been  removed.     {Sobotta  and  McMurrich.) 

The  m.  transversus  thoracis,  or  triangularis  sterni,  is  within  the 
thoracic  cavity.  It  arises  from  the  dorsal  surface  of  the  xiphoid 
process  and  most  of  the  body  of  the  sternum  and  is  inserted  into  the 
second,  third,  fourth,  fifth  and  sixth  costal  cartilages  of  both  sides. 

The  diaphragm  (diaphragma)  is  a  musculomembranous  partition 
between  the  thorax  and  abdomen.  The  muscular  portion  arises  as 
follows:  dorsally  by  two  crura  (pars  lumbal  is)  the  rig/it  crus  arising 
from  the  first,  second  and  third  lumbar  vertebras  and  the  left  from 
the  first  and  second  lumbar  vertebra;;  from  the  middle  arcuate  liga- 
ment in  front  of  the  aorta;  from  the  internal  arcuate  ligament  (arcus 
lumbocostalis  medialis)  that  stretches  from  the  body  of  the  first 
lumbar  vertebra  to  its  transverse  process;  from  the  external  arcuate 


1 68 


/  i  game at  (arc  its  lumbocostal  is  lateralis)  that  stretches  from  the 
transverse  process  of  the  first  lumbar  vertebra  to  the  apex  and 
lower  margin  of  the  twelfth  rib.  Ventrally,  the  diaphragm  arises 
from  the  dorsal  surface  of  the  ensiform  cartilage  of  the  sternum 
{pars  sternalis)  and  from  the  dorsal  surface  of  the  six  lower  costal 
cartilages;  laterally,  it  arises  from  the  lower  six  ribs  (pars  costalis). 
The  muscle  fibers  are  all  inserted  into  the  central  tendon. 

The  centra!  tendon  (centrum  tendincum)  consists  of  three  leaflets 
of  which  the  right  is  the  largest  and  the  left  the  smallest.  There  are 
three  chief  openings  in  the  diaphragm.  The  aortic  orifice  (hiatus 
aorticus)  is  the  lowest  and  most  dorsal;  it  transmits  the  aorta,  the 


Fig.  132. — The  abdominal  surface  of  the  diaphragm.  .4,  Middle  arcuate  ligament  and 
aortic  orifice;  B.  esophageal  orifice;  C,  caval  orifice;  D.  right  crus;  E,  medial  arcuate  ligament; 
F,  lateral  arcuate  ligament. 

vena  azygos  major  and  the  thoracic  duct.  The  esophageal  orifice 
(hiatus  esophageus)  is  to  the  left  of  the  preceding  and  at  a  more 
ventral  level;  it  transmits  the  esophagus  and  vagal  nerves.  The 
caval  orifice  (foramen  vena  cavce)  is  the  highest  and  is  situated  to  the 
right  of  the  midline.  It  is  quadrate  in  form  and  transmits  the 
inferior  vena  cava. 

The  diaphragm  is  dome-shaped  and  when  viewed  from  the  side 
shows  that  the  ventral  attachment  is  at  a  higher  level  than  the  dorsal; 
when  viewed  from  the  front  it  exhibits  two  domes  of  which  the  right 
is  the  higher,  reaching  the  level  of  the  fifth  interspace  in  the  mid- 


THE    MUSCLES    OF    THE    ABDOMEN  169 

clavicular  line;  the  left  dome  reaches  the  level  of  the  sixth  left 
sternochondral  junction.  The  position  varies  with  inspiration  and 
expiration,  its  excursion  at  times  being  as  great  as  2  inches. 

Actions. — Inspiration  is  accomplished  mainly  by  the  diaphragm 
and  intercostal  muscles  assisted  by  the  mm.  scalenei,  serrati  pos- 
teriores,  levatores  costarum  and  the  subcostal  muscles.  The  dia- 
phragm depresses  its  central  tendon  and  elevates  the  inferior  ribs. 
The  external  intercostal  muscles  elevate  the  ribs.  The  internal  inter- 
costal muscles  are  supposed  to  do  the  same.  The  accessory  muscles 
of  inspiration  are  the  mm.  pectorales,  quadratus  lumborum  sterno- 
mastoideus,  latissimus  dorsi,  infrahyoid  muscles  and  extensors  of 
the  vertebral  column. 

Expiration  is  accomplished  by  the  relaxation  of  the  above  muscles 
and  elevation  of  the  diaphragm  causing  the  thoracic  cavity  to  be- 
come smaller,  by  the  elasticity  of  the  lungs  and  by  the  contraction 
of  the  abdominal  muscles. 

THE  MUSCLES  AND  FASCIA  OF  THE  ABDOMEN 

The  superficial  fascia  of  the  abdomen  contains  a  variable  quantity 
of  fat  and  consist  of  a  single  layer  in  the  superior  portion  of  the 
abdominal  wall.  In  the  groin  region  it  is  separable  into  two  layers, 
the  superficial  one  of  which  is  continuous  with  that  of  the  thigh;  the 
deeper  layer  is  attached  to  the  inguinal  ligament  and  fascia  lata  of 
the  thigh  thus  preventing  the  passage  of  fluids  from  the  abdominal 
wall  to  the  thigh.  These  fascial  layers  also  pass  along  the  spermatic 
cord  and  form  part  of  the  scrotum. 

The  deep  fascia  is  closely  applied  to  the  muscles  even  investing 
some.     It  is  variable  in  its  thickness  in  different  regions. 

The  abdominal  cavity  side  of  the  muscles  is  covered  by  fascia 
that  is  named  according  to  the  muscle  covered  (transversalis,  quad- 
ratus lumborum,  psoas,  diaphragmatic).  At  the  thigh  it  forms  the 
femoral  sheath  for  the  femoral  vessels  and  at  the  inguinal  ring  the 
i  nf u  nd  ibul  i/orm  fascia.  Upon  the  deep  surface  of  this  fascia  are  the 
extraperitoneal  tissue  and  the  peritoneum. 

The  extraperitoneal  tissue  usually  contains  a  great  quantity  of 
fat  in  which  are  embedded  the  extraperitoneal  abdominal  organs. 
The  peritoneum  is  a  serous  membrane  that  lines  the  abdominal  cav- 
ity and  invests  some  organs  completely,  some  incompletely  and 
others  not  at  all. 

The  m.  obliquus  externus  abdominis  is  broad  and  thin  and  arises 
from  the  eight  inferior  ribs  interdigitating  with  the  mm.  serratus 
anterior  and  latissimus  dorsi.  It  is  inserted  into  the  ventral  half  of 
the  external  iliac  crest  and  aponeurosis  by  means  of  which  it  is 
attached  to  the  xyphoid  process,  the  linea  alba  and  the  symphysis 


170  MYOLOGY 

pubis.     This   aponeurosis  is   extensive  forming   various  ligaments 
and  assisting  in  forming  the  external  abdominal  ring. 

The  inguinal  ligament  (lig.  inguinale  Pouparf)  is  the  inferior 
margin  of  the  aponeurosis  of  the  m.  obliquus  externus  abdominis 
and  extends  from  the  ventral  superior  spine  of  the  ilium  to  the  tuber- 
cle of  the  pubis.  It  affords  attachment  to  some  muscles  and  also 
forms  the  floor  of  the  inguinal  canal. 


Oelto'deus 
'Clavicular  portion  of pecmaj 


Sternocostal 
portion  of  pec  ma) 


Abdominal  portion  of pec  rnaj 
Serratus  anterior 


Cremaster 
Reflected  inguinal  lig 


of  penis 
Superior  pillar  Inferior  pillar. 

Fig.  133. — Superficial  and  second  layers  of  the  abdominal  and  pectoral  muscles  seen  from 
in  front.  On  the  right  side  the  pectoralis  major  and  the  obliquus  abdominis  externus  have 
been  removed.     {Sobotta  and  McMurrich.) 


The  lig.  lacunare,  or  Gimbernat' s  lig.,  is  a  triangular  reflection  of 
the  medial  extremity  of  the  inguinal  ligament  toward  the  iliopec- 
tineal  line. 

The  subcutaneous  inguinal  ring,  or  external  abdominal  ring,  is 
just  over  the  tubercle  of  the  pubis  and  through  it  pass  the  spermatic 
cord,  or  round  ligament  of  the  uterus,  and  the  cremaster  muscle  and 


THE    MUSCLES    OF    THE    ABDOMEN 


171 


its  fascia.  The  margins  of  the  ring  are  called  the  crura  and  these 
are  thin.  From  the  margins  of  the  ring  a  thin  tubular  sheath  of 
fascia,  the  inter  columnar,  or  external  spermatic  fascia,  passes  over  the 
spermatic  cord. 

The  reflex  inguinal  ligament  of  Colles,  or  the  triangular  fascia, 
consists  of  fascial  fibers  from  the  opposite  side  that  are  attached 
to  the  crest  and  tubercle  of  the  pubis. 


Omohyoid 
Scalenus  medius 
Sternohyoid  *  *, 
+  Sternothyreoid/l. 


Fig.  134. — The  superficial  layer  of  the  abdominal  muscles  and  the  serratus  anterior  seen 
from  the  left  side.  The  pectoralis  major  and  minor  and  the  inner  portion  of  the  clavicle  have 
been  removed  and  the  arm  has  been  drawn  backward.     (Sobotta  and  McMurrich.) 


The  m.  obliquus  internus  abdominis,  broad  and  thin,  arises 
from  the  lumbodorsal  fascia,  the  ventral  two-thirds  of  the  iliac  crest 
and  from  the  lateral  portion  of  the  inguinal  ligament.  Its  fibers 
are  directed  superiorly  and  medially,  the  superior  ones  are  inserted 
into  the  three  lower  ribs  and  the  remainder  are  inserted  into  an  apo- 
neurosis that  joins  that  of  the  external  oblique  and  transversalis 
muscles.     This  conjoined  fascia  splits  to  envelop  the  rectus  abdominis 


muscle  forming,  at  the  lateral  margin  of  the  muscle  the  linea  semi- 
lunaris and  at  the  medial  margin  the  linea  alba.  The  inferior  margin 
of  the  aponeuroses  is  joined  by  fibers  from  the  transversalis  fascia 
forming  the  conjoined  tendon,  or  falx  aponeiaotica  ingiiinalis;  this  is 
attached  to  the  pubic  crest  and  iliopectineal  line. 

The  m.  cremaster  arises  from  the  inferior  margin  of  the  internal 
oblique  muscle  and  is  inserted,  in  part,  to  the  tubercle  of  the  pubis. 

The  m.  transversus  abdominis  arises  from  the  deep  surfaces  of 
the  lower  six  costal  cartilages,  the  lumbosacral  fascia,  the  medial 


External  intercostal  /tots. 


Sternal  membrane 
Rectus  abdomin 
Rib   VI 


Intercostales  interni 


Serratus  anterior 


'ntercostales  exterm 


Semicircular  line 
Transversalis  fascia 

Inouinal  lid. 
Cremaster  x 

Pyramidalis  X 


Fk;.  135. — The  deeper  layers  of  the  abdominal  muscles.  On  the  left  side  the  anterior 
layer  of  the  sheath  of  the  rectus  abdominis  and  the  obliquus  abdominis  externus  have  been 
removed;  on  the  right  side,  in  addition,  the  rectus  abdominis,  the  pyramidalis.  and  the  ob- 
liquus abdominis  internus.  The  external  intercostal  ligaments  have  been  removed  on  the 
left  side.     (Soboita  and  McMurrich.) 


crest  of  the  ilium  and  from  the  lateral  part  of  the  inguinal  ligament. 
After  a  horizontal  course  the  fibers  are  inserted  into  an  aponeurosis 
that  joins  that  of  the  internal  oblique  to  form  the  sheath  of  the 
rectus  muscle;  this  aponeurosis  is  inserted  into  the  xyphoid  cartilage, 
the  linea  alba  and  the  crest  of  the  pubis.  The  inferior  fibers  form 
the  conjoined  tendon  described  above. 

The  m.  pyramidalis  abdominis  is  small  and  arises  from  the  pubic 
crest  and  is  inserted  into  the  ilea  alba. 


THE   INGUINAL   CANAL 


173 


The  m.  rectus  abdominis  arises  from  the  symphysis  and  crest  of 
the  pubis  and  is  inserted  into  the  ventral  surface  of  the  xyphoid 
process  and  of  the  fifth,  sixth  and  seventh  costal  cartilages.  The 
muscle  is  divided  transversely  by  three  or  more  tendinous  bands, 
the  inscriptiones  tendineee.  The  lateral  margin  of  the  muscle  is  indi- 
cated by  the  lined  semilunaris.  At  this  line  the  abdominal  apo- 
neurosis splits  to  form  the  two  layers  of  the  rectus  sheath.     The  in- 


Fig.  136. — The  diaphragm  and  the  muscles  of  the  dorsal  abdominal  wall.  The  ven- 
tral abdominal  wall  and  the  abdominal  viscera  have  been  removed;  the  thorax  has  been 
bent  backward  so  that  the  lumbar  vertebra  are  strongly  convex  forward.  (Sobctta  and 
McMurrich.) 


ferior  portion  of  the  dorsal  layer  of  the  sheath  is  not  present  and  the 
linea  semicirctdaris  marks  the  inferior  limit  of  the  layer. 

The  inguinal  canal  (canalis  ingninalis)  begins  at  the  abdominal 
inguinal  ring  and  continues  to  the  subcutaneous  inguinal  ring.  The 
abdominal,  or  internal  ring,  lies  about  1  cm.  superior  to  the  middle 
of  the  inguinal  ligament.  The  floor  of  the  canal  is  formed  by  the 
inguinal  ligament;  the  ventral  vail  by  the  aponeurosis  of  the  external 


174  MYOLOGY 

oblique  and  the  muscle  fibers  of  the  internal  oblique;  the  dorsal  wall 
consists  of  the  transversalis  fascia  and  falx  aponeurotica  inguinalis 
(conjoined  tendon).  At  the  abdominal  ring  is  the  infundibuliform, 
or  internal  spermatic  fascia.  In  the  canal  lies  the  spermatic  cord 
and  it  is  invested  by  the  infundibuliform,  cremasteric  and  inter- 
columnar  fascia?. 

The  triangular  area  between  the  inguinal  ligament,  inferiorly, 
the  rectus  abdominis,  medially,  and  the  inferior  epigastic  artery, 
laterally  is  called  Hesselback's  triangle.  A  hernia  at  this  point  is 
called  a  directing  ing.  hernia,  whereas  when  the  intestine  traverses 
the  inguinal  canal  and  appears  at  the  subcutaneous  ring  then  it 
is  an  oblique  ing.  hernia. 

Actions. — To  compress  the  abdominal  wall  as  in  defecation,  vomit- 
ing, micturition,  parturition  and  deep  respiration.  They  also  act  as 
flexors  of  the  vertebral  column  and  pelvis. 

Nerve  Supply. — Pyramidalis  from  the  last  thoracic  nerve;  the  cre- 
master  from  the  genitofemoral  (L.  i,  2);  the  remainder  are  supplied 
by  the  ventral  rami  of  the  last  six  thoracic  nerves. 

The  m.  quadratus  lumborum  arises  from  the  dorsal  portion  of  the 
iliac  crest  from  the  transverse  processes  of  the  lower  lumbar  verte- 
bras and  from  the  iliolumbar  ligament;  it  is  inserted  into  the  inferior 
margin  of  the  last  ribs  and  the  transverse  processes  of  the  upper 
lumbar  vertebra;. 

Ad  ion. — Assists  in  inspiration  and  flexion  and  extension  of  the 
vertebral  column. 

Nerve  Supply. — Branches  from  the  ventral  rami  of  the  first  three 
lumbar  nerves. 

FASCIA  AND  MUSCLES  OF  THE  PERINEUM  AND  PELVIS 

The  superficial  fascia  extends  into  the  scrotum  to  form  there  the 
dartos  fascia  and  the  scrotal  septum,  in  the  male,  while  in  the  female  it 
assists  in  forming  the  mons  veneris  and  labia  majora,  containing  con- 
siderable fat  in  the  latter  places.  It  also  passes  over  the  penis  and 
connects  with  the  superficial  fascia  of  the  thigh,  buttocks  and  abdom- 
inal wall.  In  the  dorsal  part  of  the  perineum  there  is  a  considerable 
space  between  the  rectum  and  ischium  on  each  side  and  this  consti- 
tutes the  ischiorectal  fossa  which  is  filled  with  a  mass  of  fat  contained 
in  the  superficial  fascia  here.  Ventrally,  the  superficial  fascia  com- 
prises two  layers  as  in  the  groin.  The  superficial  layer  is  continuous 
with  that  of  abdomen  and  thigh.  The  deeper  layer  is  attached  to  the 
pubic  arch,  the  fascia  of  the  urinogenital  diaphragm  and  to  the  root 
of  the  penis  and  the  scrotal  septum.  The  attachment  of  this  layer 
prevents  the  urine  that  extravasates,  when  the  perineal  portion  of 
the  urethra  is  ruptured,  from  entering  the  thigh  and  the  ischiorectal 
fossa. 


THE    MUSCLES   OF    THE   PERINEUM  1 75 

The  deep  fascia  is  thin  and  tends  to  invest  the  muscles.  In  the 
midline  of  the  perineum  about  i  cm.  ventral  to  the  anal  canal,  there  is 
a  fibrous  area  called  the  central  tendinous  point  of  the  perineum  and 
four  muscles  are  here  attached. 

The  m.  sphincter  ani  externus  is  a  flattened,  spindle-shaped  muscle 
around  the  anus  and  anal  canal  connected  ventrally  with  other  mus- 
cles at  the  central  tendinous  point  and  dorsallv  it  is  connected  with 
anococcygeal  ligament. 

Action. — Closes  the  anus  voluntarily. 

Nerve  Supply. — By  the  third  and  fourth  sacral  nerves  through  the 
pudendal  and  perineal  nerves. 

The  m.  corrugator  cutis  ani  are  radiating  bundles  of  smooth  mus- 
cle tissues  at  the  margin  of  the  anal  opening  and  superficial  to  the 
external  sphincter. 

The  m.  transversus  perinei  superficialis  is  a  variable  muscle. 
When  present,  it  arises  from  the  inferior  ramus  of  the  ischium  and  the 
fascia  of  the  urinogenital  diaphragm:  it  is  inserted  into  the  central 
point  of  the  perineum. 

Action. — They_/f.v  the  central  tendinous  point  of  the  perineum. 

Nerve  Supply. — Deep  perineal  branch  of  the  pudendal  nerve  (S. 

3,4)- 

The  m.  bulbocavernosus,  or  accelerator  urlnas  of  the  male,  sur- 
rounds the  root  of  the  penis,  the  bulb  of  the  urethra  and  the  corpus 
spongiosum,  in  the  male.  It  arises  from  the  central  point  of  the 
perineum  and  median  raphe  and  the  fibers  are  inserted  into  the 
fascia  of  the  urinogenital  diaphragm,  the  dorsal  surface  of  the 
corpus  cavernosum  and  into  the  fascia  of  the  dorsum  of  the  penis. 

The  bulbocavernosus,  or  sphincter  vaginae  of  the  female  arises 
from  the  central  point  of  the  perineum  and  is  inserted  into  the  root  of 
the  clitoris  somewhat  as  in  the  male. 

Ail  ion. — Compresses  the  urethra  in  the  emission  of  semen  and  urine 
and  assists  in  the  erection  of  the  penis  in  the  male.  In  the  female  it 
contracts  the  vaginal  orifice  and  compresses  the  bulb  of  the  vestibule. 

Nerve  Supply. — Deep  branch  of  the  perineal  nerve  (S.  3,  4). 

The  m.  ischiocavernosus,  or  erector  penis,  invests  the  crus  penis 
of  the  male.  It  arises  from  the  tuberosity  of  the  ischium  and  is 
inserted  to  the  fascia  of  the  crus  penis  and  to  the  corpus  cavernosum 
of  the  penis. 

The  m.  ischiocavernosus,  or  erector  clitoridis,  of  the  female  is 
smaller  and  similar  in  attachments. 

Action. — Erection  of  penis  or  clitoris. 

Nerve  Supply. — Deep  branch  of  the  perineal  nerve  (S.  3,  4). 

The  urinogenital  diaphragm  comprises  several  muscles  and  two 
layers  of  fascia. 


176 


The  m.  sphincter  urethras  membranaceae  arises  from  the  inferior 
pubic  ramus  and  is  inserted  into  the  median  raphe  partly  ventral  and 
partly  dorsal  to  the  urethra. 

The  m.  transversus  perinei  profundus  arises  from  the  inferior 
ramus  of  the  ischium  and  is  inserted  into  the  median  raphe. 

The  m.  sphincter  urethras  in  the  female  is  smaller  and  some  of  the 
fibers  are  inserted  into  the  side  of  the  vagina  with  the  transversus 
perinei  profunda. 

Action. — Slight  compression  of  the  urethra  and  slight  constriction 
of  the  vagina. 

/ coccyx 


occygeal 
ligament 


scrotum 
corpus  cavernosum  of  urethra  ^corpora  cavernosa  of  pen* 

Fig.    137. — Superficial  muscles  of  the  male  perineum.     (Sobottu  and  McMur 


The  fascial  portion  constitutes  the  fascia  urinogenitalis  diaphrag- 
matis  inferior  et  superior.  The  inferior  fascia,  or  superficial  layer  of 
the  triangular  ligament,  tills  in  the  pubic  arch  and  is  about  3.5  cm.  in 
height.  Between  its  apex  and  the  subpubic  ligament  passes  the 
dorsal  vein  of  the  penis.  Laterally  the  fascia  is  attached  to  the  rami 
of  ischium  and  pubis.  This  fascial  layer  is  perforated  by  the  ure- 
thra, ducts  of  Cowper's  glands  and  various  arteries,  veins  and  nerves. 
In  the  female  this  fascia  is  not  as  strong  and  it  is  pierced  by  the 
vagina.  The  deep  layer,  or  fascia  diaphragmatis  urinogenitalis 
superior  is  a  portion  of  the  pelvic  fascia  and  is  perforated  by  the 
urethra.     Between  its  two  layers  are  found  the  dorsal  vein  of  the 


THE  MUSCLES  OF  THE  SUPERIOR  EXTREMITY  177 

penis,  the  membranous  part  of  the  urethra,  the  bulbocavernosus 
muscle,  the  glands  of  Cowper  and  their  ducts  and  arteries,  veins  and 
nerves  in  the  male.  In  the  female  the  dorsal  nerve  and  vessels  of  the 
clitoris,  a  part  of  the  urethra,  the  bulbocavernosus  muscle,  the  glands 
of  Bartholin,  the  vestibular  bulbs  and  arteries,  veins  and  nerves. 

The  pelvic  fascia  (fascia  pelvina)  forms  a  lining  for  the  pelvic 
cavity  and  an  investment  for  the  muscles  here.  It  is  connected, 
superiorly,  with  the  fascia  of  the  abdominal  cavity  while  inferiorly, 
it  is  attached  to  the  bony  and  ligamentous  boundary  of  the  inferior 
pelvic  outlet.  Different  portions  have  been  given  special  names ;  that 
portion  in  relation  with  the  pyriformis  muscle  is  the  pyriformis  fascia 
while  the  obturator  fascia  is  in  relation  with  the  m.  obturator  internus. 
The  fascia  diaphragmatis  urinogenitalis  superior  has  already  been 
discussed,  and  with  the  various  muscles  previously  discussed  con- 
stitutes the  ventral  portion  of  the  pelvic  floor.  The  dorsal  part  of  the 
floor  consists  of  the  mm.  levatores  ani  and  the  anal  fascia,  the  perineal 
body  and  the  anococcygeal  body.  The  white  line,  or  tendinous  arch, 
is  a  taut  band  of  fascia  that  extends  from  the  dorsal  surface  of  the 
symphysis  pubis  to  the  ischial  spine.  The  pelvic  fascia  also  forms 
the  true  ligaments  of  the  bladder  and  the  sheath  of  the  prostate 
gland. 

The  m.  levator  ani  arises  from  the  dorsal  surface  of  the  body  of  the 
pubis,  the  tendinous  arch  and  the  spine  of  the  ischium.  It  is  inserted 
into  central  tendon  of  the  perineum  into  the  external  sphincter,  to 
the  anococcygeal  ligament  and  to  the  sides  of  the  lower  coccygeal 
segments. 

Actions. — Supports  and  raises  the  pelvic  floor;  assists  in  defecation; 
elevates  the  prostate  gland,  or  contracts  the  vagina;  assists  in  child- 
birth. 

Nerve  Supply. — Directly  by  the  third  and  fourth  sacral  nerves  and 
by  branches  from  the  perineal  nerve. 

The  m.  coccygeus  arises  from  the  spine  of  the  ischium  and  the 
sacrospinous  ligament.  It  is  inserted  into  the  lateral  aspect  of  the 
inferior  portion  of  the  sacrum  and  the  superior  part  of  the  coccyx. 

Action. — Mainly  to  assist  the  levator  ani  in  supporting  the  pelvic 
floor. 

Nerve  Supply. — By  the  third  and  fourth  sacral  nerves. 

THE  SUPERIOR  EXTREMITY  OR  PECTORAL  APPENDAGE 

Fascia  and  Muscles  of  the  Pectoral  Region. — The  superficial  fascia 
is  thin  and  contains  a  variable  quantity  of  fat  and  the  mammary 
glands. 

The  deep  fascia  invests  the  pectoral  muscles  and  connects  with  the 
abdominal  fascia.     Medially,  it  is  attached  to  the  sternum,  superiorly, 


178  MYOLOGY 

to  the  clavicle  and  laterally,  forms  the  axillary  fascia.  This  fascia 
forms  the  costocoracoid  membrane  and  ligament.  The  costocoracoid 
membrane  is  a  layer  of  the  deep  fascia  extending  from  the  superior 
margin  of  the  m.  pectoralis  minor  to  the  clavicle.  This  layer,  before 
it  reaches  the  clavicle,  splits  to  envelop  the  m.  subclavius  and 
then  it  is  attached  to  the  inferior  surface  of  the  clavicle.     Medially, 


Deltoideus 
Clavicular  portion  ofpecmaj 


Sternocostal 
portion  of  pec  mat 


Cremaster 
Reflected  inguinal  lig 


Superior  pillar  Inferior  pillar. 

Fig.  138. — Superficial  and  second  layers  of  the  abdominal  and  pectoral  muscles  seen 
from  in  front.  On  the  right  side  the  pectoralis  major  and  the  obliquus  abdominis  externus 
have  been  removed.     (Sobotta  and  McMurrich.) 


this  membrane  is  attached  to  the  first  costal  cartilage  and  laterally 
to  the  coracoid  process  and  as  this  part  of  the  membrane  is  quite 
well  developed  it  is  called  the  costocoracoid  ligament.  The  membrane 
is  pierced  by  the  cephalic  vein,  the  branches  of  the  lateral  ventral 
thoracic  nerve  and  thoracoacromial  artery  and  vein. 

The  m.  pectoralis  major  is  large  and  fan-shaped,  arises  from  the 
sternal  half  of  the  ventral  margin  of  the  clavicle,  from  the  ventral 


THE  MUSCLES  OF  THE  SHOULDER  REGION        1 79 

surface  of  the  sternum  and  the  first  six  costal  cartilages  and,  a  small 
part,  from  the  aponeurosis  of  the  external  oblique  muscle.  It  is 
inserted  as  a  rather  broad  thick  tendon  into  the  lateral  margin  of 
the  intertubercular  sulcus,  or  bicipital  groove.  The  clavicular  part 
of  the  muscle  forms  the  inferior  part  of  the  tendon  while  the  costo- 
sternal  portion  forms  the  superior  part. 

Action. — Assists  in  drawing  the  arm  to  the  side  of  the  thorax;  adduc- 
tion and  medial,  or  inward  rotation  while  bringing  the  arm  across 
the  ventral  part  of  the  thorax. 

Nerve  Supply. — Lateral  ventral  thoracic  nerve,  from  the  lateral 
cord  of  the  brachial  plexus  (C.  5,  6,  7)  and  the  medial  ventral  thoracic 
nerve  from  the  medial  cord  of  the  brachial  plexus  (C.  8,  T.  1). 

The  m.  pectoralis  minor,  small  and  triangular,  arises  from  the 
ventral  surfaces  of  the  chondral  extremities  of  the  third,  fourth  and 
fifth  ribs  and  the  third  and  fourth  intercostal  fasciae;  it  is  inserted 
into  the  margin  of  the  coracoid  process  near  the  origin  of  the  mm. 
biceps  and  coracobrachialis. 

Action. — Depresses  and  draws  the  shoulder  forward. 

Nerve  Supply. — Same  as  pectoralis  major. 

The  m.  subclavius  arises  from  the  superior  surface  of  the  first 
costal  cartilage  and  sternal  end  of  the  first  rib  and  is  inserted  into 
the  subclavian  groove  on  the  inferior  surface  of  the  clavicle. 

Action. — Depresses  the  clavicle  and  shoulder  and  assists  in  inspira- 
tion by  fixing  the  first  rib. 

Nerve  Supply. — Branch  from  the  brachial  plexus  (C.  5,  6). 

The  m.  serrarus  anterior,  or  serratus  magnus,  arises  by  eight  or 
nine  digitations  from  the  first  eight  ribs  and  is  inserted  into  the  verte- 
bral margin  and  ventral  surfaces  of  the  superior  and  inferior  angles 
of  the  scapula. 

Action. — Draws  the  scapula  forward,  assists  in  rotating  the  scapula 
and  is  an  important  muscle  in  inspiration. 

Nerve  Supply. — The  long  thoracic  nerve  (from  the  ventral  rami 
of  the  fifth,  sixth  and  seventh  cervical  nerves). 

MUSCLES  OF  THE  SHOULDER  REGION 

The  m.  deltoideus,  a  large  multipennate  muscle,  arises  from  the 
lateral  third  of  the  ventral  margin  of  the  clavicle,  from  the  lateral 
margin  of  the  acromion,  from  the  inferior  margin  of  the  spine  of  the 
scapula  and  from  the  fascia  covering  the  infraspinatus  muscle.  It 
is  inserted  into  the  deltoid  tubercle  of  the  shaft  of  the  humerus. 

Action. — Abducts  the  humerus  to  a  right  angle  with  the  glenoid 
fossa  of  the  scapula.  Assists  in  drawing  the  arm  forward  (ventrally) 
and  backward  (dorsally). 

Nerve  Supply. — Axillary,  or  circumflex  nerve  (C.  5,  6). 


i8o 


The  m.  supraspinatus  arises  from  the  bulk  of  the  supraspinous 
fossa  and  the  fascia  covering  the  muscle  and  is  inserted  into  the 
proximal  facet  of  the  greater  tubercle  of  the  humerus  and  into  the 
capsular  ligament. 

Action. — Assists  the  deltoid  in  abducting  the  arm. 

Nerve  Supply. — Suprascapular  nerve  (C.  5,  6). 

The  m.  infraspinatus  arises  from  the  bulk  of  the  infraspinous 
fossa  and  the  fascia  covering  it  and  is  inserted  into  the  middle  facet 
of  the  greater  tubercle  of  the  humerus. 


Trapezius 


raspinatus 
'fascia 


Teres  major 

■issimus  X 
head  of  triceps  brachii 

brachii 


Outer  head  of  triceps  brachii 
Inner  head  of  triceps  brachii 


picondy/e 


3   Antibrachial 
1     fascia 

Fig.  i3g. — The  deltoid  and  muscles  of  the  upper  arm  see 
Mc  Munich.) 


from  the  side.     'Sobotta  i 


Action. — Assists  in  abducting  the  arm  and  when  raised  assists  in 
drawing  the  arm  dorsally. 

Nerve  Supply. — Suprascapular  nerve  (C.  5,  6). 

The  m.  teres  minor  arises  from  the  dorsal  surface  of  the  axillary 
margin  of  the  scapula  (proximal  two-thirds)  and  the  intermuscular 
septa  and  is  inserted  into  the  distal  facet  of  the  greater  tubercle  of 
the  humerus. 

Action. — Rotates  the  humerus  laterally. 


THE    FASCIA   AND    MUSCLES    OF   THE   ASM  151 

Nerve  Supply. — Axillary,  or  circumflex  nerve  (C.  5,  6). 

The  m.  teres  major  arises  from  the  inferior  third  of  the  dorsal 
aspect  of  the  axillary  margin  of  the  scapula  and  from  the  intermus- 
cular septa  and  is  inserted  into  the  medial  margin  of  the  intertuber- 
cular  sulcus  (bicipital  groove)  of  the  humerus. 

With  the  margins  of  the  teres  minor  and  subscapularis  muscles 
and  the  neck  of  the  humerus,  the  teres  major  forms  a  triangular 
space.  The  long  head  of  the  triceps  muscle  divides  this  into  a 
medial,  quadrilateral  space,  transmitting  the  axillary  nerve  and  the 
posterior  circumflex  artery  and  a  lateral,  triangular  sp^c,  transmit- 
ting the  circumflex  scapula  artery. 

Action. — Rotates  the  humerus  medially. 

Nerve  Supply. — Lower  scapular  nerve  (C.  5,  6). 


Levator  scapulae  X 

/JV R homboideus  minor  X 


Infraspinatus 
Rhomboideus  majo 


Deltoideus 
Subdeltoid  bursa 
Pect  oralis  maj> 


Fig.  140. — The  muscles  of  the  dorsal  surface  of  the  left  scapula  and  the  neighboring 
portion  of  the  extensor  surface  of  the  upper  arm.  The  deltoid  has  been  removed  with  the 
exception  of  its  origin  and  insertion;  portions  of  the  dorsal  muscles  inserting  into  the  verte- 
bral border  of  the  scapula  and  also  of  the  latissimus  dorsi  and  pectoralis  major  have  been 
retained.      (Sobottu  an  J  McMurrich.) 

The  m.  subscapularis  arises  from  the  entire  subscapular  fossa  and 
is  inserted  into  the  lesser  tubercle  of  the  humerus  and  into  the  cap- 
sular ligament  and  even  into  the  surgical  neck  of  the  bone. 

Action. — Medial  rotator  of  the  humerus  and  assists  in  drawing  the 
arm  ventrally. 

Nerve  Supply. — Long  and  short  subscapular  nerves  (both  C.  5,  6). 


FASCIA  AND   MUSCLES  OF  THE  ARM 

The   superficial  fascia   is   thin    and  presents  a   bursa    over    the 
olecranon. 

The  deep  fascia  is  continuous  with  that  of  the  shoulder  muscles 


182 


and  the  axilla  and  with  that  of  the  forearm.  It  sends  in  a  medial 
septum,  that  separates  the  brachialis  muscle  from  the  medial  head 
of  the  triceps,  and  a  thin  lateral  septum,  that  separates  the  brachialis 
and  brachioradialis  muscles  from  the  triceps,  behind.  These  septa 
are  only,  in  the  distal  half  of  the  arm  and  are  attached  to  the  epicon- 
dyles  distally. 

OmohuoideuB  X 

~  -Clavicle 


Coracoid 

process. 


Subscapular, 


Subclavivsx 


Bursa  of  latissirrtus 
Tendon  of  larissimus 

pecrora/i's  major 
Deltoideus  x 


>  head  of  biceps 


-The  muscles  of  the  flexor  surface  of  the  upper  arm,  superficial  layer.     The  deltoid 
has  been  removed.      (Sobotta  and  .1/.  Murrich.) 


The  m.  coracobrachialis  arises  in  common  with  the  short  head  of 
the  biceps  muscle,  from  the  tip  of  the  coracoid  process  of  the  scapula 
and  is  inserted  about  the  middle  of  the  medial  margin  of  the  humerus. 

A  ction. — A  ssists  the  biceps  in  ra  ising  and  drawing  the  arm  medially. 

Nerve  Supply. — Musculocutaneous  nerve  (C.  7). 

The  m.  biceps  brachii  arises  from  the  tip  of  the  coracoid  process 
(short  head,  or  caput  breve)  and  from  the  supraglenoid  tuberosity 
and  glenoid  ligament  (long  head,  or  caput  longum).  The  latter  tendon 
passes  through  the  shoulder  joint  and  into  the  bicipital  groove  and 
then  forms  a  fleshy  belly  that  lies  beside  the  belly  from  the  short 


VENTRAL   MUSCLES   OF   THE   FOREARM   AND  HAND  1 83 

head;  these  form  a  common  tendon  that  is  inserted  into  the  dorsal 
surface  of  the  tubercle  of  the  radius.  The  bicipital  fascia  (laccrtus 
fibrosus)  is  a  strong  fascial  band  that  arises  from  the  tendon  in  front 
of  the  elbow  joint  and  passes  medially  to  join  the  deep  fascia  of  the 
forearm. 

Action. — Draws  the  humerus  forward  at  the  shoulder  joint,  flexes 
the  elbow  joint  and  supinates  the  forearm. 

Nerve  Supply. — The  musculocutaneous  nerve  (C.  5,  6). 

The  m.  brachialis  (anterior)  arises  from  the  distal  two-thirds  of 
the  ventral  surface  of  the  humerus  and  the  intermuscular  septa  and 
is  inserted  into  the  ventral  ligament  of  the  elbow  joint  and  the  coro- 
noid  process  of  the  ulna. 

Action. — Flexes  the  forearm  at  the  elbow. 

Nerve  Supply. — Musculocutaneous  nerve  (C.  5,  6)  and  radial 
nerve  (C.  5,  6). 

The  m.  triceps  brachii,  the  only  dorsal  muscle  of  the  arm,  arises 
by  three  heads.  The  long  head  (caput  longum)  arises  from  the  infra- 
glenoid  tuberosity  of  the  scapula;  the  lateral  head  arises  from  the 
lateral  margin  (proximal  one-third)  and  the  intermuscular  septa; 
the  medial  head  has  the  most  extensive  origin  from  the  dorsal  sur- 
face of  the  shaft  of  the  humerus  and  the  intermuscular  septa.  The 
common  tendon  is  inserted-  into  the  tip  of  the  olecranon  process  of 
the  ulna  and  into  the  deep  fascia  of  the  forearm  on  each  side  of  this. 

Action. — Mainly  an  extensor  of  the  forearm;  the  long  head  may 
assist  in  adducting  the  humerus  at  the  shoulder-joint. 

Nerve  Supply. — Branches  from  the  radial  nerve  of  the  dorsal  cord 
of  the  brachial  plexus  (C.  6,  7,  8). 

FASCUE   AND   VENTRAL   MUSCLES   OF  THE  FOREARM   AND   HAND 

The  superficial  fascia  is  as  usual  containing  fat  and  the  superficial 
vessels  and  nerves.     It  contains  one  muscle  in  the  palm. 

The  m.  palmaris  brevis,  in  the  medial  side  of  the  palm,  arises 
from  the  medial  margin  of  the  central  palmar  aponeurosis  and  is 
inserted  into  the  skin  of  the  medial  border  of  the  hand.  It  wrinkles 
the  skin  here,  when  acting,  and  deepens  the  hollow  of  the  hand. 

The  deep  fascia  is  quite  strong  at  the  elbow  region  due 'to  reinforce- 
ment from  the  tendon  of  the  biceps  and  triceps  muscles.  It  sends 
in  intermuscular  septa  one  of  which  is  attached  to  the  dorsal  margin 
of  the  ulna.  At  the  wrist  it  is  strengthened  by  transverse  bands 
that  form  important  ligaments.  The  transverse  carpal,  or  anterior 
annular  ligament  (lig.  carpi  transvcrsum).  is  a  broad  band  stretching 
between  the  navicular  and  greater  multangular  bones,  laterally,  and 
the  pisiform  and  hamate  bones,  medially.  This  holds  the  flexor 
tendons  and  median  nerve  in  place.     The  space  between  the  bones 


184  MYOLOGY 

and  the  ligament  is  divided  into  two  compartments,  the  larger  for 
the  flexor  tendons  of  the  digits  and  the  median  nerve,  and  the  smaller 
for  the  flexor  carpi  radialis '  tendon.  Three  synovial  sheaths  lie 
beneath  this  ligament. 

The  dorsal  carpal,  or  posterior  annular  ligament  (lig.  carpi  dor  sale), 
is  another  broad  ligamentous  band  upon  the  dorsal  surface  of  the 
wrist  joint.  Beneath  it  are  six  compartments  each  lined  with  a  syn- 
ovial membrane.  These  are,  lateromedially,  as  follows:  (a)  mm.  ab- 
ductor pollicis  longus  and  extensor  pollicis  brevis;  (b)  mm.  extensores 
carpi  radialis  longus  and  brevis;  (c)  m.  extensor  pollicis  longus;  (d) 
mm.  extensores  digitorum  communis  and  indicis  proprius;  (e)  m. 
extensor  digiti  quinti  proprius;  (/)  m.  extensor  carpi  ulnaris. 

In  the  palm  the  deep  fascia  constitutes  the  palmar  aponeurosis. 
The  medial  part  of  this  is  the  largest  and  most  extensive  as  well  as 
the  strongest  portion.  It  is  triangular  in  shape  with  its  apex  blending 
with  lig.  carpi  transversum;  its  base  is  opposite  the  bases  of  the  four 
medial  digits  and  here  a  slip  is  given  off  for  each  finger;  each  slip 
divides  into  two  slips  that  are  attached  to  the  sides  of  the  metacar- 
pophalangeal joints  and  the  first  phalanx  of  each  finger.  The  digital 
sheaths  are  continuations  of  the  palmar  aponeurosis  upon  the  ventral 
surface  of  each  finger.  Each  sheath  is  attached  to  the  sides  of  the 
phalanges  and  serves  to  keep  the  flexor  tendons  in  place.  Each  is 
lined  with  a  synovial  membrane.  The  synovial  space  of  the  little  finger 
is  continuous  with  the  large  synovial  sac  of  the  palm  that  also  extends 
into  the  forearm  under  the  transverse  carpal  ligament.  The  synovial 
spaces  of  the  outer  three  fingers  are  independent  of  one  another. 
The  synovial  space,  or  sheath  of  the  thumb  extends  through  the 
palm  and  under  the  transverse  carpal  ligament  into  the  forearm. 

SUPERFICIAL  MUSCLES  OF  THE  FOREARM 

The  m.  pronator  teres  arises  from  the  medial  epicondylic  ridge  and 
its  intermuscular  septum,  from  the  medial  epicondyle  of  the  humerus 
and  the  fascia  over  it  and  from  intermuscular  septa  here;  this  con- 
stitutes the  caput  humeralc.  The  caput  ulnare,  or  deep  head  arises  from 
the  medial  surface  of  the  coronoid  process  of  the  ulna.  The  muscle 
is  inserted  into  the  middle  of  the  lateral  surface  of  the  shaft  of  the 
radius. 

.  1 1  lion. — Flexes  the  elbow  joint  and  pronates  the  forearm. 

Nerve  Supply. — Median  nerve  (C.  6). 

The  m.  flexor  carpi  radialis  arises  from  the  medial  condyle  through 
the  common  tendon,  from  the  intermuscular  septa  and  fascia  over  it 
and  is  inserted  into  the  proximal  extremities  of  the  second  and  third 
metacarpal  bones. 

Action. — Flexes  the  elbow  and  wrist  joints  and  assists  in  pronating 
the  forearm. 


THE  VENTRAL  MUSCLES  OF  THE  FOREARM 


I85 


Nerve  Supply. — Median  nerve  (C.  6). 

The  m.  palmaris  longis  arises  from  the  common  tendon  of  the 
medial  epicondyle,  the  fascia  over  it  and  the  intermuscular  septa  and 
is  inserted  into  the  transverse  carpal  ligament  and  the  apex  of  the 
palmar  aponeurosis. 

Action. — Assists  inflexion  of  the  elbow  and  wrist  joints  and  makes 
the  palmar  fascia  tense. 

Nerve  Supply. — Median  nerve  (C.  6). 


Brack  /o  radial  is 


Tendon  of  biceps 


Fig.  142.  Fig.  143. 

Fig.  142. — The  superficial  layer  of  the  muscles  of  the  flexor  surface  of  the  forearm  to- 
gether with  the  brachioradialis.  seen  from  in  front.     'Sobotto  and  M,  Murrich.) 

Fig.  143. — The  superficial  layer  of  the  muscles  of  the  flexor  surface  of  the  forearm  after 
removal  of  the  palmaris  longus  and  the  flexor  carpi  radialis.  seen  from  in  front  and  slightly 
from  the  radial  side.  The  brachioradialis  is  drawn  outward  to  show  e  supinator  and  the 
insertion  of  the  tendon  of  the  biceps.      (Sobotta  and  McMurrich.) 

The  m.  flexor  carpi  ulnaris  arises  from  the  common  tendon  of  the 
medial  epicondyle  of  the  humerus,  the  fascia  over  it  and  the  inter- 
muscular septa  and  from  the  medial  margin  of  the  olecranon  and  the 
first  two-thirds  of  the  dorsal  margin  of  the  ulna.  The  muscle  is  in- 
serted into  the  pisiform  and  hamate  bones  and  the  proximal  extremity 
of  the  fifth  metacarpal  bone. 


l86  MYOLOGY 

Action. — Flexes  and  addticts  the  wrist  and  assists  in  flexing  the 
elbow  joint. 

Nerve  Supply. — Ulnar  nerve  (C.  8,  Th.  i). 

The  m.  flexor  digitorum  sublimis  has  three  heads.  The  caput 
humerale  arises  from  the  common  tendon,  the  ulnar  collateral  liga- 
ment and  from  the  intermuscular  septa.  The  caput  radiale  arises 
from  the  first  two-thirds  of  the  ventral  surface  of  the  radius.  The 
caput  ulnare  arises  from  the  medial  margin  of  the  coronoid  process 
of  the  ulna.  All  join  to  form  a  common  belly  that  divides  in  the 
distal  third  of  the  forearm  and  continues  as  four  tendons  which  at  the 
wrist  are  arranged  in  pairs,  middle  and  ring  fingers  (superficial)  and 
index  and  little  fingers  (deep).  Here  these  tendons  are  contained  in 
a  common  synovial  sheath  with  the  tendons  of  the  profundus  muscle. 
In  the  palm  the  four  tendons  separate  and  over  the  base  of  the  first 
phalanx  of  each  finger  the  tendons  split  to  give  passage  to  the  cor- 
responding tendon  of  the  flexor  digitorum  profundus  muscle.  Dor- 
sal to  the  latter  tendon  these  slips  partially  reunite  to  be  inserted 
into  the  sides  of  the  second  phalanges  of  the  fingers.  The  vincida 
longa  and  brevia.  are  delicate  accessory  portions  of  each  tendon. 

Action. — Flexes  the  elbow,  wrist,  metacarpophalangeal  and  first 
interphalangeal  joints. 

Nerve  Supply. — Median  nerve  (C.  6). 

DEEP  LAYER 

The  m.  flexor  digitorum  profundus  arises  from  the  ventral  and 
medial  surfaces  of  the  ulna  and  olecranon  (first  two-thirds)  and 
from  the  middle  third  of  the  medial  half  of  the  interosseous  mem- 
brane and  the  deep  fascia.  Its  broad  tendon  passes  beneath  the 
transverse  carpal  ligament  and  in  the  palm  divides  into  four  tendons 
for  the  four  fingers.  Each  tendon  passes  through  the  split  in  the 
corresponding  tendon  of  the  m.  flexor  digitorum  sublimis  and 
is  inserted  into  the  ventral  surface  of  the  base  of  the  distal  phalanx. 
Each  tendon  also  gives  off  vinculo  longa  and  brevia. 

The  mm.  lumbricales  are  four  small  muscles  connected  with  the 
tendons  of  the  preceding  muscle  in  the  palm.  Each  of  the  two  lateral 
muscles  arises  by  a  single  head  from  the  radial  side  of  the  tendon  for 
the  index  and  middle  fingers  and  is  inserted  into  the  side  of  the  cap- 
sule of  the  metacarpophalangeal  articulation  and  into  the  side  of  the 
corresponding  extensor  tendon  dorsally.  Each  of  the  two  medial 
muscles  arises  by  two  heads  from  the  adjacent  sides  of  the  second, 
third  and  fourth  tendons  and  is  inserted  in  the  same  manner. 

Action. — The  flexor  digitorum  profundus  flexes  the  wrist  and  the 
fingers  at  all  of  their  joints.  The  lumbricales  flex  the  fingers  at  the 
metacarpophalangeal  joints  and  assist  in  extending  the  fingers  at  their 
interphalangeal  joints. 


THE   VENTRAL    MUSCLES   OF    THE    FOREARM 


I87 


Nerve  Supply. — Flexor  digitorum  profundus:  Volar  interosseous 
branch  of  the  median  nerve  (C.  7,  8,  Th.  1)  and  the  ulnar  nerve 
(C.  8,  Th.  1).  The  two  lateral  lumbricales:  Median  nerve  (C.  6,  7). 
The  two  medial  lumbricales:  Ulnar  nerve  (C.  8,  Th.  1). 

The  m.  flexor  pollicis  longus  arises  from  the  middle  third  of  the  ven- 
tral surface  of  the  shaft  of  the  radius  and  from  the  medial  margin  of 
the  coronoid  process  of  the  ulna.  It  is  inserted  by  means  of  a  long 
tendon  that  passes  beneath  the  carpal  ligament,  in  its  own  synovial 
sheath,  to  the  base  of  the  distal  phalanx  of  the  thumb. 


Bicipito-  radial  bursa 

Supinator 


-r-  Radial  head  of  flexor 

pollicis  lonous 


Tendon  of  extensor 
Tendon  of  flexor  _LIIIK|i.    Ill  carpi  radial,  lonous 
carpi  ulnaris  J  >  W.V  ^1,',    Tondon    0f  flexor 

idialis 
i 
Tendon  of  patmaris  lonous 

Fig.  144. — The  deep  layer  of  the  muscles  of  the  flexor  surface  of  the  forearm  after  removal  of 
the  superficial  layer,  seen  from  in  front.     (Sobotta  and  McMurrich.) 

Action. — Flexes  the  wrist  and  the  thumb. 

Nerve  Supply. — Volar  interosseous  branch  of  the  median  nerve 
(C.  7,  8,  Th.  1.). 

The  m.  pronator  quadratus  arises  from  the  ventral  surface  and  me- 
dial margin  of  the  distal  quarter  of  the  ulna  and  passing  transversely 
across  the  forearm  is  inserted  into  the  distal  quarter  of  the  ventral 
surface  of  the  radius. 

Action. — Assists  in  pronating  the  forearm. 

Nerve  Supply.- — Volar  interosseous  branch  of  the  median  nerve 
(C.  7,  8,  Th.  1). 


SHORT  MUSCLES  OF  THE  THUMB 

The  m.  abductor  pollicis  brevis  arises  from  the  tubercle  of  the 
navicular  and  the  greater  multangular  bones  and  from  the  transverse 
carpal  ligament.  It  is  inserted  into  the  first  phalanx  of  the  thumb 
(radial  side)  and  into  the  capsule  of  the  metacarpophalangeal  joint. 

Action. — Abducts  the  thumb. 

Xcrve  Supply. — Median  nerve  (C.  6,  7). 

The  m.  opponens  pollicis  arises  from  the  transverse  carpal  ligament 
and  the  ridge  of  the  greater  multangular  bone.  It  is  inserted  into  the 
ventral  surface  and  lateral  margin  of  the  first  metacarpal  bone. 


An+ibrachiat 
fascia 


Tendon  of palrnaris   hnous 


r  aponeurosis  and  the  palma 
■  shown  covered  by  the  fasci: 


brevis.     The  thenar  and  hypothenar 
(Sobotlo.  and  McMurrich.) 


Action. — Draws  the  metacarpal  bone  over  the  palm. 

Nerve  Supply. — Median  nerve  (C.  6,  7). 

The  m.  flexor  pollicis  brevis  consists  of  two  parts  of  which  the 
superficial  portion  arises  chiefly  from  the  transverse  carpal  ligament 
and  is  inserted  into  the  radial  side  of  the  base  of  the  first  phalanx  of 
the  thumb.  The  deep  portion,  or  first  palmar  interosseous  muscle, 
arises  from  the  base  of  the  first  metacarpal  bone  (medial  side).  It 
is  inserted  into  the  medial  side  of  the  base  of  the  first  phalanx  of  the 
thumb. 

Action. — Flexes  the  thumb  and  assists  in  opposing  it  to  the  fingers. 

Nerve  Supply. — Median  nerve  (C.  6,  7). 

The  m.  adductor  pollicis  also  consists  of  two  parts.     The  oblique 


THE    MUSCLES    OF    THE    LITTLE    FINGER  189 

head-  arises  from  the  ventral  surface  of  the  greater  and  lesser  mult- 
angular and  the  capitate  bones  and  from  the  bases  of  the  second, 
third  and  fourth  metacarpal  bones  and  their  ligaments.  It  is  in- 
serted into  the  medial  side  of  the  base  of  the  first  phalanx  of  the 
thumb. 

The  transverse  head  arises  from  the  median  ridge  of  the  ventral 
aspect  of  the  third  metacarpal  bone  and  the  fascia  covering  the 
adjacent  interosseous  muscles.  It  is  inserted  into  the  medial  side  of 
the  base  of  the  first  phalanx  of  the  thumb. 

Action. — Adducts  the  thumb  and  assists  in  opposing  it  to  the 
fingers. 

Nerve  Supply. — Deep  branch  of  the  ulnar  nerve  (C.  8,  Th.  i). 

MUSCLES  OF  THE  LITTLE  FINGER 

The  m.  abductor  digiti  quinti  arises  from  the  pisiform  bone  and  the 
tendon  of  the  flexor  carpi  ulnaris  muscle.  It  is  inserted  into  the 
medial  side  of  the  base  of  the  first  phalanx  of  the  little  finger. 

Action. — Draws  the  little  finger  from  the  ring  finger  and  flexes  it 
at  the  metacarpophalangeal  joint. 

Nerve  Supply. — Deep  branch  of  the  ulnar  nerve  (C.  8,  Th.  i). 

The  m.  opponens  digiti  quinti  arises  from  the  transverse  carpal  liga- 
ment and  the  hamate  bone.  It  is  inserted  into  the  medial  margin 
and  medial  half  of  the  ventral  surface  of  the  fifth  metacarpal  bone. 

.  1 1  lion. — Draws  the  metacarpal  forward  so  as  to  deepen  the 
hollow  of  the  hand. 

Nerve  Supply. — Deep  branch  of  the  ulnar  nerve  (C.  8,  Th.  i). 

The  m.  flexor  digiti  quinti  brevis  arises  from  the  transverse  carpal 
ligament  and  the  hamate  bone  and  is  inserted  into  the  medial  side 
of  the  first  phalanx  of  the  little  finger. 

Action. — Flexes  the  proximal  phalanx  of  the  little  finger. 

Nerve  Supply. — Deep  branch  of  the  ulnar  nerve  (C.  8,  Th.  i). 

There  are  two  sets  of  interosseous  muscles,  palmar  and  dorsal. 

The  mm.  interossei  volares,  or  palmar  interossei,  are  three  in  num- 
ber. Each  arises  by  one  head:  the  first  arises  from  the  medial  side 
of  the  second  metacarpal  bone,  the  second  and  third  from  the  lateral 
sides  of  the  fourth  and  fifth  metacarpal  bones.  The  first  is  inserted 
into  the  extensor  tendon,  the  capsule  of  the  metacarpophalangeal 
joint  and  the  medial  side  of  the  first  phalanx  of  the  second  finger. 
The  second  and  third  are  inserted  into  the  lateral  sides  of  the  first 
phalanges  of  the  fourth  and  fifth  fingers  and  their  respective  extensor 
iendons  and  capsular  ligaments. 

The  mm.  interossei  dorsales  axe  jour  in  number.  Each  arises  by 
a  head  from  each  of  the  two  bones  that  bound  its  interosseous  space. 
The  first  is  inserted  into  lateral  side  of  the  first  phalanx  of  the  index 


190  MYOLOGY 

finger  and  its  extensor  tendon.  The  second  is  inserted  in  the  same 
manner  to  the  middle  linger.  The  third  is  inserted  into  the  medial 
side  of  the  same  finger  and  the  fourth  into  the  medial  side  of  the  ring 
finger. 

Action. — The  dorsal  intcrossei  abduct  the  fingers  from  a  line  through 
the  middle  finger  while  the  palmar  muscles  adduct  the  fingers  to  this 
line.  The  interossei  also  assist  the  lumbricales  to  flex  the  first 
phalanges  at  the  metacarpophalangeal  joint  and  extend  the  second 

Tendon  of fle/tor  oto prof. 


Annular  fibres 

<f<>3    ' 


•Flexor  dqit.V 
Ooponens  di<f.V 
Transverse  carpal 
ligarnenrlf 
Abductor  c/ifVX 
Pisiform  bone 
Tendon  of  flexor 
~<lrpi  ulndr/iX 


Tendon  of- flexor 
carpi  nsdra/a 


subhmh 


Fig.  14- 


aponeurosis, 
(.Sobolta  and  McMurri 


The  tendo 
■h.) 


Fig.   146. 

Fig.  146. — The  palmar  muscles  after  removal  of  the  pain 
sheath  of  the  middle  finger  has  been  split  lengthwi: 

Fig.  147. — The  deep  layer  of  the  palmar  muscles.  The  transverse  carpal  ligament  and 
the  abductores  digiti  V  and  pollicis  brevis  have  been  removed.  The  tendons  of  the  long 
flexors  have  been  removed  from  the  carpal  canal  and.  after  splitting  the  tendon-sheaths  of 
the  fingers,  have  been  partly  removed  and  partly  drawn  aside.     (Sobolta  and  McMurrich.) 

and   third  phalanges    through    their   attachment    to    the    extensor 
tendons. 

Nerve  Supply. — Deep  branch  of  the  ulnar  nerve  (C.  8,  Th.  1). 


DORSAL  AND  LATERAL  MUSCLES  OF  THE  FOREARM 

The  superficial  muscles  are  seven  in  number. 

The  m.  brachioradialis  arises  from  the  lateral  epicondylic  ridge 
(proximal  two-thirds)  and  from  the  intermuscular  septum.  It  is 
■inserted  at  the  beginning  of  the  groove  upon  the  lateral  side  of  the 
distal  extremity  of  the  radius. 

Action. — Flexes  the  elbow  joint,  assists  the  pronators  and  supina- 
tors and  is  a  semipronator  and  a  semisupinator. 


THE   DORSAL    MUSCLES    OF   THE    FOREARM 


I9I 


Nerve  Supply. — Branch  from  the  radial  nerve  (C.  5,  6). 

The  m.  extensor  carpi  radialis  longus  arises  from  the  distal  third 
of  the  lateral  epicondylic  ridge,  from  the  intermuscular  septum  and 
from  the  common  tendon  of  the  lateral  epicondyle.  It  is  inserted 
into  the  radial  side  dorsal  surface  of  the  base  of  the  second  meta- 
carpal bone. 

Action. — Extends  the  wrist  and  assists  in  flexing  the  elbow. 


Fie 


Fig.  148. 
-The  superficial  layer  of 


1  carpi  radial,  brevis 
Tendon  of  exrensori$  carpi  radial,  hnpi 

Fig.  149. 
nuscles  of  the  extensor  surface  of  the  forearm 


(Sobotla 


148.- 
and  McMurrich.) 

Fig.  140. — The  deep  layer  of  muscles  of  the  extensor  surface  of  the  forearm.  The  super- 
ficial layer  of  the  extensors  has  been  removed,  the  cavities  of  the  dorsal  carpal  ligament  have 
been  opened  and  the  tendons  of  the  superficial  muscles  removed.      (Sobotla  and  McMurrich.) 


Nerve  Supply. — Radial  nerve  (C.  5,  6,  7,  8). 

The  m.  extensor  digitorum  communis  arises  from  the  common 
tendon,  from  the  lateral  epicondyle  of  the  humerus,  from  the  fascia 
of  the  region  and  the  intermuscular  septa.  Near  the  wrist  it  con- 
tinues as  four  tendons  that  pass  beneath  the  dorsal  carpal  ligament 
with  the  tendon  of  the  extensor  indicis  proprius.  Upon  the  dorsum 
of  the  palm  the  tendons  separate  and  pass  toward  the  dorsal  surface 


192  MYOLOGY 

of  each  finger.  Over  the  first  phalanx  of  each  finger  the  tendon 
receives  the  tendons  of  the  interossei  and  lumbricales  muscles.  At 
the  distal  extremity  of  the  first  phalanx  each  tendon  separates  into 
three  portions,  the  median  of  which  is  inserted  into  the  base  of  the 
second  phalanx.  The  lateral  slips  unite  and  are  inserted  into  the 
base  of  the  third  phalanx.  Upon  the  dorsum  of  the  palm  the  second 
and  third,  and  the  third  and  fourth  tendon  are  connected  to  each 
other  bv  an  oblique  tendinous  slip,  which  interferes  with  the  indi- 
vidual extension  of  these  fingers. 

Action. — Extends  the  elbow,  wrist  and  fingers. 

Nerve  Supply. — Dorsal  interosseous  nerve  (C.  5,  6,  7,  8). 

The  m.  extensor  carpi  radialis  brevis  arises  from  the  common  ten- 
don, the  intermuscular  septa  and  fascia  and  the  radial  collateral 
ligament.  It  is  inserted  into  the  dorsal  surface  of  the  bases  of  the 
second  and  third  metacarpal  bones. 

Action. — Extends  the  wrist  and  assists  in  flexing  the  elbow. 

Nerve  Supply. — Deep  branch  of  the  radial  nerve  (C.  5,  6). 

The  m.  extensor  digiti  quinti  proprius  arises  from  the  common 
tendon,  the  fascia  over  it  and  the  intermuscular  septa.  It  is  in- 
serted into  the  expansion  of  the  tendon  of  the  extensor  digitorum 
communis  over  the  first  phalanx  of  the  little  finger. 

Action. — Extends,  elbow,  wrist  and  little  finger. 

Nerve  Supply. — Dorsal  interosseous  nerve  (C.  6,  7,  8). 

The  m.  extensor  carpi  ulnaris  arises  from  the  common  tendon, 
the  fascia  over  the  muscle,  the  intermuscular  septa  and  from  the 
middle  half  of  the  deep  fascia  attached  to  the  dorsal  margin  of  the 
ulna.  It  is  inserted  into  the  medial  surface  of  the  base  of  the  fifth 
metacarpal  bone. 

Action. — Extends  and  adducts  the  wrist  and  assists  in  extension  of 
the  elbow  joint. 

Nerve  Supply. — Dorsal  interosseous  nerve  (C.  5,  6,  7,  8). 

The  m.  anconeus,  a  small  triangular  muscle,  arises  from  the  dorsal 
surface  of  the  lateral  epicondyle  of  the  humerus  and  the  capsular 
ligament  and  is  inserted  into  the  lateral  surface  of  the  olecranon  and 
the  dorsal  surface  of  the  proximal  part  of  the  ulna  to  the  oblique  line. 

Action. — Extends  the  elbow  joint. 

Nerve  Supply. — Radial  nerve  (C.  7,  8). 

The  deep  muscles  are  Jive  in  number. 

The  m.  supinator  (brevis)  arises  from  the  lateral  epicondyle  of 
the  humerus,  the  collateral  and  annular  ligaments  of  the  joint,  the 
fascia  over  it  and  from  the  surface  of  the  ulna  just  distal  to  the  radial 
notch.  It  is  inserted  to  the  lateral  and  ventral  surface  of  the  radius 
from  the  neck  to  the  oblique  line. 

Action. — Main  supinator  of  the  forearm  and  extends  the  elbow. 

Nerve  Supply. — ^eep  branch  of  the  radial  nerve  (C.  7,  8). 


THE   DORSAL    MUSCLES    OF   THE    FOREARM 


193 


The  in.  abductor  pollicis  longus,  or  extensor  ossi  metacarpi  pollicis, 

arises  from  the  proximal  part  of  the  lateral  half  of  the  dorsal  surface 
of  the  ulna,  from  the  middle  part  of  the  dorsal  surface  of  the  radius 
and  from  the  intervening  part  of  the  interosseous  membrane.  It  is 
inserted  into  the  lateral  side  of  the  base  of  the  first  metacarpal  bone. 

Action. — Abducts  the  metacarpal  bone  of  the  thumb,  and  assists 
in  abducting  and  extending  the  wrist. 

Nerve  Supply. — Dorsal  interosseous  nerve  (C.  6,  7,  8). 

The  m.  extensor  pollicis  longus  arises  from  the  middle  part  of  the 
dorsal  surface  of  the  ulna  and  the  interosseous  membrane  and  is 
inserted  into  the  dorsal  surface  of  the  second  phalanx  of  the  thumb. 

Action. — Extends  and  abducts  the  thumb  and  wrist. 


Tendon   of  extensor 
pollicis  tono'us 

Tendon  of  extensor 
carpi  radiaiis  brevis 


Fig.  150. — Tendons  and  muscles  (interossei  dorsales)  of  the  dorsum  of  the  hand.  The  dor- 
sal carpal  ligament  is  retained,  the  rest  of  the  dorsal  fascia  being  removed.  {Sobotta  and 
Mc  Munich.) 

Nerve  Supply. — Dorsal  interosseous  nerve  (C.  5,  6,  7,  8). 

The  m.  extensor  pollicis  brevis  arises  from  the  distal  part  of  the 
dorsal  surface  of  the  radius  and  from  the  adjoining  portion  of  the 
interosseous  membrane.  It  is  inserted  into  the  dorsal  surface  of  the 
base  of  the  first  phalanx  of  the  thumb. 

Action. — Extends  and  abducts  the  thumb  and  wrist. 

Nerve  Supply. — Dorsal  interosseous  nerve  (C.  5,  6,  7,  8). 

The  m.  extensor  indicis  proprius  arises  from  the  dorsal  surface  of 
the  ulna  (just  distal  to  the  extensor  pollicis  longus)  and  from  the 
interosseous  membrane.  It  is  inserted  into  the  index  finger  by  join- 
ing the  tendon  of  the  m.  extensor  communis  digitorum. 

Action. — Extends  the  index  finger  and  the  wrist. 

Nerve  Supply. — Dorsal  interosseous  nerve  (C.  5,  6,  7,  8). 


194  MYOLOGY 

THE  INFERIOR  EXTREMITY,  OR  PELVIC  APPENDAGE 
FASCLE  AND  MUSCLES  OF  THE  BUTTOCK  AND  THIGH 

The  superficial  fascia  of  the  buttock  and  thigh  is  continuous  with 
the  fascia  of  the  adjoining  parts  of  the  body.  In  the  buttocks  it 
contains  a  large  quantity  of  fat  which  gives  these  parts  their  full 
appearance.  In  the  inguinal  region,  or  groin,  the  superficial  fascia 
consists  of  a  superficial  and  a  deep  layer;  the  superficial  layer  contains 
considerable  fat  and  the  superficial  vessels  and  nerves.  The  deep 
layer  is  attached  to  the  medial  half  of  the  inguinal  ligament,  to  the 
pubic  arch  (medially)  to  the  deep  fascia  of  the  thigh  (laterally)  and 
below,  it  joins  the  superficial  layer.  By  its  attachment  to  the 
inguinal  ligament  and  pubic  arch  fluids  of  the  perineum  and 
abdominal  wall  are  prevented  from  passing  into  the  thigh.  Between 
these  two  layers  of  superficial  fascia  are  seen  the  superficial  inguinal 
lymph  nodes,  the  great  saphenous  vein  and  its  tributaries. 

The  deep  fascia,  or  fascia  lata,  invests  the  muscles  and  vessels  of 
the  thigh  and  buttock.  Superiorly  (proximally)  it  is  attached  to 
the  pubic  symphysis  and  crest,  the  inguinal  ligament,  the  iliac  crest, 
the  sacrotuberous  ligament,  the  ischium  and  the  pubic  arch ;  inf eriorly 
(distally)  it  is  attached  to  the  patella,  the  condyles  of  the  tibia,  the 
head  of  the  fibula,  forms  the  collateral  ligaments  of  the  patella  and 
is  continuous  with  the  deep  fascia  of  the  leg.  The  ventral  and  lateral 
portions  of  this  fascia  are  thick  and  strong  and  in  the  distal  part  of 
the  thigh  it  sends  in  muscular  septa.  Near  the  pubic  region  the 
fascia  is  pierced  by  the  great  saphenous  vein  and  this  area  constitutes 
the  fossa  ovalis,  or  saphenous  opening.  This  is  oval  in  shape  and  cov- 
ered by  the  fascia  cribrosa  and  superficial  fascia.  The  lateral  margin 
of  the  fossa,  margo  falciformis,  is  sharp,  while  the  medial  margin  is 
shelf-like  and  is  called  the  fascia  pectinea.  This  is  attached,  supe- 
riorly, to  the  iliopectineal  line  and  capsule  of  the  hip  joint  after  pass- 
ing dorsal  to  the  femoral  sheath  and  over  the  muscles  here.  The 
distal  margin  of  the  fossa  is  called  the  inferior  cornu.  The  proximal 
margin  is  the  superior  cornu.  The  lateral  portion  of  the  fascia  shows 
a  band-like  thickening  that  is  called  the  tractus  iliotibialis,  or  ilio- 
tibial  band  into  which  the  m.  tensor  fascia?  lata;  and  part  of  the  m. 
gluteus  maximus  are  inserted.  The  distal  portion  of  this  band 
strengthens  the  knee  joint  laterally.  The  lateral  intermuscular  sep- 
tum extends  medially  from  the  fascia  lata,  separates  the  ventral  and 
dorsal  muscles  and  is  attached  to  the  linea  aspera  and  the  lateral 
epicondylic  line.  The  medial  intermuscular  septum  passes  laterally 
and  is  attached  to  the  linea  aspera  and  the  medial  epicondylic  line 
and  forms  the  ventral  wall,  or  roof  of  the  adductor  canal.  Over 
most  of  the  buttock  this  fascia  is  thick. 

The  femoral    sheath  is  a  cone-shaped  prolongation  of  the  iliac 


THE  VENTRAL   MUSCLES   OF   THE   THIGH  I95 

(dorsaily)  and  transversalis  fasciae  (ventrally)  into  the  thigh.  It 
contains  the  femoral  vessels  and  is  divided  into  three  compartments: 
the  medial  compartment,  or  femoral  canal  contains  some  fat,  the  inter- 
mediate the  femoral  vein  and  the  lateral  one  the  femoral  artery. 
The  abdominal  opening  of  the  femoral  canal  constitutes  the  femoral 
ring.  That  portion  of  the  inguinal  ligament  ventral  to  the  ring  is 
called  the  superficial  femoral  arch,  while  the  thickened  part  of  the 
femoral  sheath  under  cover  of  the  inguinal  ligament  is  called  the  deep 
femoral  arch.  The  tissues  that  fill  the  ring  constitute  the  femoral 
septum.     The  femoral  sheath  is  about  1V2  inches  in  length. 

VENTRAL  MUSCLES  OF  THE  THIGH 

The  m.  sartorius  arises  from  the  ventral  superior  spine  of  the  ilium 
and  the  notch  below,  passes  to  the  medial  side  of  the  thigh  and  is 
inserted  into  the  superior  extremity  of  the  tibia  just  below  the  medial 
condyle;  it  also  is  attached  to  the  capsular  ligament  and  the  fascia 
lata.  It  is  a  strap-like  muscle  and  forms  the  lateral  boundary  of  the 
femoral  triangle. 

Action. — Flexes  the  knee  and  everts  the  thigh. 

Nerve  Supply. — The  two  intermediate  cutaneous  branches  of  the 
femoral  nerve  (L.  2,  3). 

The  m.  quadriceps  femoris  is  composed  of  four  muscles. 

The  m.  rectus  femoris  arises  by  two  heads,  one  from  the  ventral 
inferior  spine  of  the  ilium  and  the  other  from  the  roughened  area  of 
the  acetabulum.  The  two  heads  join  and  ultimately  form  a  tendon 
that  is  inserted  into  the  superior  or  proximal  margin  of  the  patella. 

The  m.  vastus  lateralis,  or  externus,  has  an  extensive  origin  from 
the  capsule,  the  hip  joint,  tubercle  of  the  femur,  from  the  margin  of 
the  great  trochanter,  from  the  gluteal  tuberosity,  part  of  the  linea 
aspera,  from  the  fascia  lata  and  the  intermuscular  septum.  It  is 
inserted  into  the  lateral  margin  of  the  patella  and  tendon  of  the  rectus 
femoris  and  into  the  capsular  ligament  of  the  knee  joint. 

The  m.  vastus  medialis,  or  interims,  arises  from  the  spiral  line,  the 
linea  aspera,  the  part  of  the  line  leading  from  this  to  the  medial  con- 
dyle, from  the  membranous  roof  of  the  adductor  canal,  from  the  in- 
termuscular septum  and  from  the  tendon  of  the  adductor  magnus. 
It  is  inserted  into  the  medial  margin  of  the  patella  and  the  rectus 
femoris  tendon  and  the  capsular  and  lateral  ligaments  of  the  knee 
joint. 

The  m.  vastus  intermedius,  or  crureus,  arises  from  the  ventral  and 
lateral  surfaces  (proximal  two-thirds)  of  the  femur,  the  intermuscular 
septum  and  from  the  end  of  the  linea  aspera  and  line  leading  to  the 
lateral  condyle.  It  is  inserted  into  the  deep  surfaces  of  the  preceding 
three  tendons. 


196  MYOLOGY 

The  m.  articularis  genu,  or  subcrureus,  arises  from  the  distal  por- 
tion of  the  ventral  surface  of  the  femur  and  is  inserted  into  the  capsule 
of  the  knee  joint. 

The  real  insertion  of  the  quadriceps  femoris  is  the  tubercle  of  the 
tibia  by  means  of  ligamentum  patellae,  the  patella  being  a  sessamoid 
bone. 

Action. — The  muscle  as  a  whole  extends  the  leg.  The  rectus  femoris 
also  flexes  the  hip  joint.  The  articularis  genu  draws  the  capsule  and 
synovial  sheaths  out  of  the  way  during  extension  of  the  leg. 


Patellar  /ig. — 3 
Tuberosity  of  tibia 


Pes 
anserinus 


Fig.  i si.  Fig.  152. 

Fig.  151, — The  superficial  layer  of  muscles  of  the  ventral  surface  of  the  thigh.  (Sobotta 
and  McMurrich.) 

Fig.  152. — The  muscles  of  the  ventral  surface  of  the  thigh  after  removal  of  the  sartorius. 
The  inguinal  ligament  has  also  been  removed.     (Sobotta  and  McMurrich.) 


Nerve  Supply. — Branches  of  the  femoral  nerve  supply  each  indi- 
vidual division  (L.  3,  4). 

The  m.  iliopsoas  consists  of  three  parts. 

The  m.  psoas  major  arises  from  the  last  thoracic  and  the  first  four 
lumbar  intervertebral  discs  and  the  margins  of  the  adjacent  verte- 
brae, from  tendinous  arches  over  the  bodies  of  the  first  four  lumbar 


THE   MEDIAL  MUSCLES   OF   THE   THIGH  197 

vertebrae  and  from  the  transverse  processes  of  all  of  the  lumbar  ver- 
tebras. A  spindle-shaped  muscle  is  formed  the  tendon  of  which  is 
inserted  into  the  apex  of  the  lesser  trochanter  of  the  femur. 

The  m.  psoas  minor  is  often  absent  but  when  present  it  arises  from 
the  last  thoracic  intervertebral  discs  and  the  margins  of  the  adjacent 
vertebras  and  is  inserted  into  the  iliopectineal  line. 

The  m.  iliacus  is  a  fan-shaped  muscle  that  arises  from  the  margin 
of  the  iliac  fossa,  the  ala  of  the  sacrum  and  the  neighboring  pelvic 
ligaments  and  from  the  capsule  of  the  hip  joint.  It  is  inserted  into 
the  lateral  portion  of  the  psoas  tendon,  the  lesser  trochanter  and  the 
neighboring  part  of  the  shaft  of  the  femur  and  into  the  capsule  of  the 
hip  joint  (m.  iliocapsularis). 

Actions. — The  psoas  muscles  flexes  the  vertebral  column  ventrally 
and  laterally.  The  iliopsoas  flexes  the  thigh  upon  the  pelvis,  or  vice 
versa. 

Nerve  Supply. — Psoas  minor,  first  and  second  lumbar  nerves;  psoas 
major,  second  and  third  lumbar  nerves;  iliacus,  femoral  nerve  (L. 

2,  3,  4)- 

The  m.  pectineus  arises  from  the  iliopectineal  line  and  bony  surface 
adjacent,  from  the  lig.  lacunare  (Gimbernat's)  and  the  fascia  over  the 
muscle.  It  is  inserted  into  the  proximal  half  of  the  line  from  the  lesser 
trochanter  to  the  linea  aspera. 

Actions. — Adducts  and  assists  in  flexing  the  thigh. 

Nerve  Supply. — Femoral  nerve  (L.  2,  3)  and  obturator  nerve  (L. 
2,  3)- 

MEDIAL  MUSCLES  OF  THE  THIGH 

The  m.  gracilis,  long  and  slender,  arises  from  the  inferior  half  of  the 
pubic  symphysis  and  the  margin  of  the  pubic  arch.  It  is  inserted 
into  the  proximal  and  medial  extremity  of  the  shaft  of  the  tibia  dorsal 
to  the  m.  sartorius  and  ventral  to  the  m.  semitendinosis. 

Actions. — Adducts,  flexes  and  rotates  the  thigh  medially. 

Nerve  Supply. — Obturator  nerve  (L.  2,  3). 

The  m.  adductor  longus  arises  from  the  ventral  surface  of  the  body 
of  the  pubic  bone  between  the  crest  and  symphysis.  It  is  inserted 
into  the  medial  lip  of  the  linea  aspera  (medial  two-fourths). 

Actions. — Adducts  and  assists  in  flexing  the  thigh. 

Nerve  Supply. — Obturator  nerve  (L.  2,  3). 

The  m.  adductor  brevis  arises  from  the  body  and  first  portion  of  the 
inferior  ramus  of  the  pubic  bone.  It  is  inserted  into  the  distal  por- 
tion of  the  line  from  the  lesser  trochanter  to  the  linea  aspera,  dorsal  to 
the  pectineus. 

Actions. — Addicts  and  flexes  the  thigh. 

Nerve  Supply. — Obturator  nerve  (L.  2,  3,  4). 

The  m.  adductor  magnus  is  the  largest  of  this  group  and  arises 


from  the  lateral  margin  and  inferior  surface  of  the  tuberosity  of  the 
ischium,  from  the  margin  of  the  inferior  ramus  of  the  ischium  and  the 
ventral  surface  of  the  inferior  ramus  of  the  pubic  bone.  It  is  in- 
serted into  the  femur  superior  to  the  linea  aspera  and  continues  all 
along  the  linea  aspera  and  the  line  leading  to  the  medial  epicondyle  of 
the  femur  and  its  adductor  tubercle;  is  is  also  attached  to  the  medial 
intermuscular  septum.     Where  the  medial  epicondylic  line  begins 


Iliopsoas  X 

Pectineus  X 


Sacrotuberous  ho. 
Adductor  lonous  X 
Gracilis  X 


Tendon  of  sartoriuS 

Tendon  of  Gracilis  ■ 

Tendon  of  semitendinosus 


Pes  anserinus 
Fig.   153- — The  deep  layer  of  n 
sartorius,   rectus  femoris,    pectineus,   add 
{Sobotta  and  McMurrich.) 


Semimembranosus 

Internal  intermuscular 
septum 

Sartorial  bursa 

Anserine  bursa 

Gastrocnemius 


the  medial  surface  of  the  thigh.      The  iliopsoas, 
:tor   longus,    and    gracilis    have    been   removed. 


there  is  a  gap  in  the  insertion  for  the  transmission  of  the  femoral 
vessels. 

Actions. — Adducts  and  extends  the  thigh. 

Nerve  Supply. — Medial  portion,  tibial,  or  internal  popliteal  nerve 
(L.  4,  5,  S.  i).    Lateral  portion,  obturator  nerve  (L.  3,  4). 

The  m.  obturator  externus  arises  from  the  inferior  half  of  the  mar- 
gin of  the  obturator  foramen  (ischium  and  pubis)  and  from  the  ad- 


THE  MUSCLES  OF  THE  BUTTOCK  199 

jacent  portion  of  the  obturator  membrane.     It  is  inserted  into  the 
fossa  on  the  medial  side  of  the  greater  trochanter. 

Actions. — Rotates  the  thigh  laterally  and  assists  inflexion  and  ad- 
duction of  the  thigh. 

Nerve  Supply. — Obturatur  nerve  (L.  3,  4). 

The  trigonum  femorale,  or  Scarpa's  triangle,  is  located  on  the  ven- 
tral surface  of  the  proximal  portion  of  the  thigh.  Its  base  is  formed 
by  the  inguinal  ligament,  its  lateral  boundary  by  the  sartorius  muscle 
and  the  media!  boundary  by  the  adductor  longus  muscle.  Its  floor 
is  formed  by  the  iliopsoas,  pectineus,  the  adductor  longus  and  some- 
times a  part  of  the  adductor  brevis  muscles.  It  contains  the  femoral 
vessels  and  nerve. 

The  adductor,  or  Hunter's  canal  (canalis  adductorius  Hunteri),  is  in 
the  medial  side  of  the  middle  third  of  the  thigh  and  is  bounded  ven- 
trally,  or  superficially  by  the  sartorius  muscle  and  fascia  between  the 
vastus  medialis  and  the  adductor  muscles;  dorsally  and  medially  by 
the  vastus  medialis.  It  contains  the  femoral  artery  and  vein  and  the 
saphenous  nerve. 

MUSCLES  OF  THE  BUTTOCK 

The  m.  gluteus  maximus  is  a  large  quadrilateral  muscle  composed 
of  very  coarse  fibers.  It  arises  from  the  iliac  bone  above  the  dorsal 
gluteal  line,  from  the  dorsal  surfaces  of  the  sacrum  and  coccyx  and 
the  sacrotuberous  ligament  and  from  the  tendon  of  the  sacrospinalis 
muscle.  It  is  inserted  into  the  gluteal  tuberosity  of  the  femur  but 
mainly  into  the  fascia  lata. 

Actions. — Extends  the  thigh  and  assists  in  adduction  and  lateral  ro- 
tation (inferior  fibers). 

Nerve  Supply. — Inferior  gluteal  nerve  from  the  sacral  plexus  (L. 
5,  S.  1,  2). 

The  m.  tensor  fasciae  latas  arises  from  iliac  crest  near  the  ventral 
superior  spine  and  the  fascia  covering  it  and  is  inserted  into  the  fascia 
lata  at  the  level  of  the  greater  trochanter. 

Actions. — Assists  in  abduction  and  rotation  of  the  thigh  and  in  sup- 
porting the  knee  joint  when  in  extension. 

Nerve  Supply. — Superior  gluteal  nerve  of  the  sacral  plexus  (L. 
4,  5.  S.  1). 

The  m.  gluteus  medius  arises  from  the  ilium  between  the  dorsal 
and  ventral  gluteal  lines  and  the  iliac  crest  and  the  fascia  over  it. 
It  is  inserted  into  the  dorsosuperior  portion  of  the  greater  trochanter. 

Actions. — Abducts  and  rotates  the  thigh  medially. 

Nerve  Supply. — Superior  gluteal  nerve  from  the  sacral  plexus 
(L.  4,  5,  S.  1). 

The  m.  gluteus  minimus  arises  from  the  ilium  between  the  ventral 
and  inferior  gluteal  lines.  It  is  inserted  into  the  ventral  surface  of 
the  greater  trochanter. 


Actions. — Abducts  the  thigh.  The  ventral  fibers  produce  medial 
rotation  and  the  dorsal  fibers  lateral  rotation. 

Nerve  Supply. — The  superior  gluteal  nerve  from  the  sacral  plexus. 

The  m.  pyriformis  arises  from  the  ventral  surface  of  the  roots  of 
the  vertebral  arches  of  the  second,  third  and  fourth  sacral  segments 
and  from  the  grooves  here,  from  the  superior  margin  of  the  sacro- 
sciatic  notch  and  ligament.  It  is  inserted  into  the  depression  on  the 
medial  surface  of  the  greater  trochanter  of  the  femur. 

Actions. — Abducts  and  rotates  the  thigh  laterally. 


Ghtaeus    medius 
(Gluteal  fascia) 


Sacrospinous  Piriformis 


Glutaeofemoral 


lliotibial  band 

Fig.    154- 

Fig.  154- — Superficial  layer  of  the  dorsal  muscles  of  the  hip. 
ficial  layer  of  the  fascia  lata  which  covers  the  tensor  fasciae 
X.  position  of  greater  trochanter.     (Sobotta  and  McMurrich.) 

Fig.  155. — Middle  layer  of  the  dorsal  muscles  of  the  thigh, 
been  divided  and  reflected.      (Sobotta  and  McMurrich.) 


Nerve  Supply. — Branches  from  the  ventral  rami  of  the  first  and 
second  sacral  nerves. 

The  m.  obturator  internus  arises  from  the  margin  of  the  obturator 
foramen  (pelvic  side),  form  the  hip  bone  superior  and  dorsal  to  the 
foramen,  from  the  obturator  membrane  and  the  fascia  over  the  mus- 
cle. It  is  inserted  into  a  small  facet  upon  the  medial  surface  of  the 
greater  trochanter. 

The  m.  gemelus  superior  arises  from  the  lateral  surface  of  the 
ischial  spine  and  is  inserted  into  the  superior  margin  of  the  tendon 
of  the  obturator  internus  muscle. 

The  m.  gemellus  inferior  arises  from  the  superior  aspect  of  the 


THE  DORSAL  MUSCLES  OF  THE  THIGH  201 

ischial  tuberosity  and  is  inserted  into  the  inferior  margin  of  the  tendon 
of  the  obturator  internus  muscle. 

Actions. — Abduct  and  rotate  the  thigh  laterally. 

Nerve  Supply. — Obturator  internus  and  superior  gemellus,  special 
branch  of  the  sacral  plexus  (S.  i,  2,  3).  The  inferior  gemellus,  a 
branch  from  the  nerve  to  the  quadratus  femoris  muscle  from  the 
sacral  plexus  (L.  4,  5,  S.  1). 

The  m.  quadratus  femoris  arises  from  lateral  margin  of  the  ischial 
tuberosity  and  is  inserted  into  the  quadrate  line  and  tubercle  of  the 
dorsal  aspect  of  the  femur. 

Actions. — Add  nets  and  rotates  the  thigh  laterally. 
Nero  Supply. — Special  nerve  from  the  sacral  plexus  (L.  4,  5,  S.  1). 

MUSCLES  (HAMSTRING)   ON  THE  DORSAL  PART  OF  THE  THIGH 

The  m.  biceps  femoris  has  two  heads  of  which  the  long  one  arises 
from  inferomedial  facet  of  the  ischial  tuberosity  in  conjunction  with 
the  semitendinosis.  The  short  head  arises  from  the  entire  lateral  lip 
of  the  linea  aspera  and  the  bulk  of  the  lateral  epicondylic  line  and 
from  the  lateral  intermuscular  septum.  The  fibers  of  the  short 
head  join  the  tendon  of  the  long  head  and  this  tendon  is  inserted  into 
the  head  of  the  fibula  and  the  lateral  condyle  of  the  tibia. 

Actions. — Flexes  the  leg  and  rotates  it  laterally  when  semiflexed 
and  when  acting  from  the  fibula  assists  in  extending  the  pelvis  upon 
the  thigh  (raises  it  from  a  stooping  position). 

Nerve  Supply. — Sciatic  nerve  through  the  tibial  division  (L.  5, 
S.  1,  2). 

The  m.  semitendinosis  arises  in  conjunction  with  the-  long  head 
of  the  biceps  from  the  tuberosity  of  the  ischium  (medial  facet).  It 
is  inserted  into  the  medial  surface  of  the  proximal  extremity  of  the 
tibia  dorsal  to  the  sartorius  and  below  the  gracilis;  it  is  also  attached 
to  the  deep  fascia  of  the  leg. 

Actions. — Flexes  and  rotates  the  leg  medially  and  extends  the  pelvis. 

Nerve  Supply. — Tibial  nerve  (L.  5,  S.  1.  2). 

The  m.  semimembranosus  arises  from  the  lateral  facet  of  the 
tuberosity  of  the  ischium  and  is  inserted  into  the  groove  upon  the 
medial  side  of  the  medial  condyle  of  the  tibia  and  by  extensions  to 
the  tibial  collateral  ligament,  the  popliteal  fascia  and  the  dorsal  sur- 
face of  the  lateral  condyle  of  the  femur  (oblique  popliteal  ligament). 

Actions. — Flexes  and  rotates  the  leg  medially  and  assists  in  exten- 
sion of  the  pelvis. 

Nerve  Supply. — Tibial  nerve  (L.  5,  S.  1,  2). 

THE  FASCLE  AND  MUSCLES  OF  THE  LEG  AND  FOOT 

The  superficial  fascia  is  the  same  as  elsewhere,  in  the  leg,  but  in 
the  foot  pads  of  fat  are  placed  under  the  heel  and  the  balls  of  the  toes. 


The  deep  fascia  is  continuous  with  that  of  the  thigh  and  around 
the  knee  joint  it  is  especially  well  developed.  Here  it  forms  the 
collateral  patellar  ligaments  and  the  (dorsal)  popliteal  fascia  which  is 
reinforced  by  the  expansions  of  the  various  neighboring  tendons. 
In  the  leg  two  intermuscular  septa  are  found  laterally  and  these  en- 
close the  peronei  muscles  separating  them  from  the  extensor,  ven- 
trally,  and  the  flexors,  dorsally.  At  the  ankle  the  deep  fascia  is  also 
strengthened  forming  the  annular  ligaments. 


Glutaeus  maximus 


Gemellus  super. 

Sacrotuberous 
Sacrospinal 
Obturator  inte, 
Bursa  of-  obturator  int. 


Glutaeus  mediuS 


Glutaeus  minimus 
Tendon  of 
bturator  internuS  X 

Middle  oluteal 

bursa 
Glutaeus  medius  a 


Gemellus  infei 
Quadratic  fem 
'Adductor  min 


Glutaeu 
Adductor  mao'nus 
Kastus  lateralis 


Popliteal  fossa 


Tendon  of  bleep* 
Gastrocnemius 


Fig.  156. — The  deep  layer  of  the  dorsal  hip  muscles  and  the  superficial  layer  of  the 
flegors  of  the  thigh  region.  The  gluteus  maximus)  and  mediusand  the  obturator  internus 
have  been  removed.     (.Sobotta  and  McMurrich.) 


The  ligamenhim  transversum  cruris,  or  ventral  annular  ligament  is 
broad  and  extends  between  the  two  malleoli.  It  holds  the  tendons 
of  the  tibialis  anterior  and  extensor  muscles  of  the  toes  in  place. 

The  ligamentum  crucial  urn  cruris,  or  lower  band  of  the  ventral  annular 
ligament  is  a  fascial  band  upon  the  dorsum  of  the  foot.  A  part  of  this 
band  holds  the  tendons  of  the  tibialis  anterior,  the  extensor  longus 
hallucis  and  the  extensor  digitorum  longus  and  peroneus  tertius 


THE   VENTRAL   MUSCLES   OF    THE    LEG  203 

muscles  in  place.  A  synovial  sheath  surrounds  each  of  these  tendons 
except  the  last  which  is  included  with  the  third  tendon. 

The  superior  peroneal  retinaculum,  or  lateral  annular  ligament  con- 
nects the  lateral  malleolus  and  the  calcaneus.  This  holds  the  pero- 
neal tendons  in  place  and  has  one  synovial  sheath. 

The  ligamentum  laciniatum,  or  medial  annular  ligament  connects 
the  medial  malleolus  with  the  tuberosity  of  the  calcaneus.  It  gives 
attachment  to  certain  muscles,  is  pierced  by  the  calcaneal  vessels 
and  nerves  and  the  dorsal  tibial  vessels  and  nerve;  it  also  holds  the 
tendons  of  the  tibialis  posterior,  flexor  digitorum  longus  and  flexor 
hallucis  longus  muscles  in  place.  Each  tendon  has  a  separate  syno- 
vial sheath. 

In  the  sole  of  the  fool  the  deep  fascia  forms  the  plantar  aponeurosis. 
The  central  portion  is  the  largest  and  strongest  part.  It  is  triangular 
in  shape  and  is  attached  dorsally,  to  the  tuberosity  of  the  calcaneus; 
near  the  toes  the  base  of  the  triangle  gives  off  five  slips,  one  for  each 
toe.  Each  slip  joins  the  digital  sheath  and  splits  into  two  portions 
each  of  which  is  attached  to  the  opposite  side  of  the  first  phalanx  of 
the  same  toe.  This  central  aponeurosis  is  of  assistance  in  maintaining 
the  arch  of  the  foot.  The  deep  fascia  on  each  side  of  the  central 
part  is  thin  and  at  the  junction  of  each  with  the  central  portion  an 
intermuscular  septum  is  sent  into  the  depths  separating  the  various 
muscles  and  forming  sheaths  for  others.  The  digital  sheaths  are 
arranged  like  those  of  the  hand. 

MUSCLES  OF  THE  VENTRAL  PART  OF  THE  LEG  AND  OF  THE  DORSUM 
OF  THE  FOOT 

The  m.  tibialis  anterior  arises  from  the  lateral  condyle  of  the  tibia, 
from  the  upper  two-thirds  of  the  lateral  surface  of  the  shaft,  from 
the  interosseous  membrane  and  intermuscular  fascia.  The  long 
tendon  passes  over  the  medial  side  of  the  dorsum  of  the  foot  and  is 
inserted  on  the  medial  side  of  the  first  cuneiform  and  first  metatarsal 
bones. 

Actions.- — Flexes  the  foot  dorsally  and  assists  in  inverting  the  foot. 

Nerve  Supply. — Deep  peroneal  nerve  (L.  4,  5,  S.  1). 

The  m.  extensor  digitorum  longus  arises  from  the  lateral  condyle 
of  the  tibia,  from  the  medial  surface  of  the  shaft  of  the  fibula  (ventral 
part)  and  from  the  fascia  and  intermuscular  septum.  It  is  inserted 
into  the  four  lesser  toes.  Over  the  first  phalanx  of  each  toe  each 
tendon  is  joined  by  tendons  from  the  lumbricales,  interossei  and  the 
extensor  digitorum  brevis.  This  conjoined  tendon  splits  into  three 
portions,  the  central  one  of  which  is  inserted  into  the  distal  phalanx 
and  the  two  side  tendons  into  the  middle  phalanx. 

Actions. — Flexes  the  foot  dorsally  and  extends  the  four  lesser  toes. 


204 


Nerve  Supply. — Deep  peroneal  nerve  (L.  4,  5,  S.  1). 

The  m.  peroneus  tertius  arises  with  the  preceding  from  the  medial 
surface  of  the  shaft  of  the  tibia  and  the  intermuscular  septum  and  is 
inserted  into  the  dorsal  surface  of  the  base  of  the  fifth  metatarsal 
bone. 

Actions. — Flexes  the  foot  dorsally  and  raises  the  lateral  margin  of 
the  foot. 


CapXulum  of  fibula  -  P 


Tibialis  anten 


Perortaeus  landus 


Patellar  Hi. 
Pes  anserinus 

Tuberosity  of  tibia 


Tendo 
of  peronaeus  III 


Tendon  of  ext 
hall.  lono. 


Fig.   157. — The  muscles  of  the  ventral  surface  of  the  lower  leg  and  of  the  dorsum  of  the  foot. 
The  transverse  crural  ligament  has  been  removed.      (Sobolta  and  McMurrich.) 

The  m.  extensor  hallucis  longus  rises  from  the  middle  two-thirds 
of  the  medial  surface  (ventral  part)  of  the  fibula  and  from  the  inter- 
osseous membrane.  The  tendon  passes  over  the  dorsum  of  the  foot 
and  is  inserted  into  the  base  of  the  distal  phalanx  of  the  great  toe. 

Actions. — Extends  the  great  toe  and  flexes  the  foot  dorsally. 

Nerve  Supply. — Deep  peroneal  nerve. 

The  m.  extensor  digitorum  brevis  arises  from  the  dorsal  surface  of 
the  calcaneus  and  from  the  lig.  cruciatum  cruris.  Its  four  tendons 
are  inserted  into  the  four  inner  toes.  The  innermost  tendon  is  in- 
serted into  the  base  of  the  first  phalanx  of  the  great  toe  while  the 


THE  DORSAL  MUSCLES  OF  THE  LEG  205 

other  three  tendons  join  the  long  extensor  tendons  of  the  next  three 
toes. 

Action. — Extends  the  four  inner  toes. 

Nerve  Supply. — Deep  peroneal  nerve. 

LATERAL  MUSCLES  OF  THE  LEG 

The  m.  peroneus  longus  arises  from  the  head  and  upper  two-thirds 
of  the  lateral  surface  of  the  fibula  and  from  the  intermuscular  septa. 
It  is  inserted  into  the  first  cuneiform  bone  and  the  base  of  the  fifth 
metacarpal  bone  (lateral  aspect).  The  tendon  passes  behind  the  lat- 
eral malleolus,  over  the  side  of  the  calcaneus  and  through  a  groove 
in  the  cuboid  bone  on  its  way  to  the  sole  of  the  foot. 

Actions. — Everts  the  foot,  extends  the  foot  and  strengthens  the 
arch. 

Nerve  Supply. — Superficial  peroneal  nerve  (L.  4,  5,  S.  1). 

The  m.  peroneus  brevis  arises  from  the  distal  half  of  the  lateral 
surface  of  the  fibula  and  intermuscular  septum.     It  is  inserted  into 
the  tuberosity  on  the  base  of  the  fifth  metatarsal  bone. 
■  Actions. — Extends  and  everts  the  foot. 

Nerve  Supply. — Superficial  peroneal  nerve. 

DORSAL  MUSCLES  OF  THE  LEG 

The  superficial  muscles  are  three  in  number  the  gastrocnemius, 
the  soleus,  constituting  the  m.  triceps  suraz,  and  the  plantaris. 

The  m.  plantaris  arises  from  the  lateral  epicondyle  of  the  femur  and 
the  adjacent  part  of  the  popliteal  surface  and  is  inserted  into  the  tendo 
calcaneus  (Achillis)  or  the  tuberosity  of  the  calcaneus. 

Ac/ions. — Assists  in  flexing  the  leg  and  extending  the  foot. 

Nerve  Supply. — Tibial  nerve  (L.  4,  5,  S.  1). 

The  m.  gastrocnemius  arises  by  two  heads.  The  medial  head 
arises  from  the  politeal  surface  of  the  femur  close  to  the  medial 
epicondyle  and  from  the  capsular  ligament  of  the  knee  joint.  The 
lateral  head  arises  from  the  dorsolateral  portion  of  the  lateral  con- 
dyle of  the  femur  and  the  epicondylic  line  and  from  the  capsular 
ligament.  Each  head  is  inserted  into  a  broad  membrane  that  forms 
the  tendo  calcanea  (Achillis)  which  is  inserted  into  the  dorsal  surface  of 
the  calcaneus. 

Actions. — Flexes  the  leg  and  extends  the  foot. 

Nerve  Supply. — Tibial  nerve  (S.  1,  2). 

The  m.  soleus  arises  from  the  upper  dorsal  surface  of  the  head  and 
shaft  of  the  fibula,  from  the  tendinous  arch  over  the  popliteal  vessels 
and  tibial  nerve  and  from  the  oblique  line  of  the  tibia.  It  is  inserted 
into  the  tendo  calcanea,  not  far  from  the  heel. 


206 


MYOLOGY 


Actions. — Extends  the  foot. 

Nerve  Supply. — Tibial  nerve  by  two  branches;  that  to  the  super- 
ficial surface  is  from  the  first  and  second  sacral  nerves;  that  for  the 
deep  surface  is  from  the  fifth  lumbar  and  first  and  second  sacral 
nerves. 

The  deep   muscles  are  four  in  number. 


158.  Fig.  159.  Fig.  160. 

Fig.   158. — The  superficial  muscles  of  the  calf  of  the  leg.      {Sobotla  and  McMurrich.) 
Fig.  159. — The  second  layer  of  the  calf  muscles.     The  gastrocnemius  has  been  removed. 

(.Sobotla  and  McMurrich.) 

Fig.   160. — The  deep  musculature  of  the  calf,  seen  from  behind  and  from  the  inner  side. 

The  triceps  sune  has  been  removed.     (Sobolta  and  McMurrich.) 

The  m.  politeus  arises  from  the  lateral  epicondyle  of  the  femur  and 
is  inserted  into  the  dorsal  surface  of  the  tibial  proximal  to  the  oblique 
line. 

Actions. — Flexes  and  rotates  the  leg  medially. 

Nerve  Supply. — Tibial  nerve  (L.  4,  5,  S.  1). 

The  m.  flexor  digitorum  longus  arises  from  the  medial  part  of  the 
dorsal  surface  of  the  tibia  below  the  oblique  line  and  from  the  in- 
termuscular septa.     It  is  inserted  into  the  base  of  the  last  phalanx  of 


THE  MUSCLES  OF  THE  SOLE  OF  THE  FOOT       207 

the  four  outer  toes.  The  tendons  pass  through  the  split  tendons  of 
the  flexor  digitorum  brevis.  With  this  muscle  the  lumbricales  and 
the  quadratus  plantae,  or  accessorius  muscles  are  associated. 

Actions. — Flexes  the  four  outer  toes  and  extends  the  foot. 

Nerve  Supply. — Tibial  nerve  (L.  5,  S.  1). 

The  m.  flexor  hallucis  longus  arises  from  the  lower  or  distal  half  of 
the  dorsal  surface  of  the  fibula  and  from  the  fascia  and  intermuscular 
septa.     It  is  inserted  into  the  base  of  the  last  phalanx  of  the  great  toe. 

Actions. — Flexes  the  great  toe,  extends  the  foot  and  assists  in 
supporting  the  arch  of  the  foot. 

Nerve  Supply. — Tibial  nerve  (L.  5,  S.  1,  2). 

The  m.  tibialis  posterior  arises  from  the  lateral  part  of  the  dorsal 
surface  of  the  tibia,  from  the  interosseous  membrane,  from  the  medial 
surface  of  the  fibula  and  from  the  intermuscular  septa.  The  tendon 
passes  into  the  sole  of  the  foot  and  has  a  very  extensive  insertion  as 
follows:  into  the  plantar  surfaces  of  the  navicular,  first  and  second 
cuneiform  bones;  into  the  plantar  surfaces  of  the  second,  third  and 
fourth  metatarsal  bones;  the  groove  of  the  cuboid  and  the  medial 
margin  of  the  sustentaculum  tali  of  the  calcaneus. 

Actions. — Extends  and  inverts  the  foot. 

Nerve  Supply. — Tibial  nerve  (L.  5,  S.  1). 

THE  MUSCLES  OF  THE  SOLE  OF  THE  FOOT 

The  plantar  muscles  are  usually  described  as  arranged  in  four 
layers. 

First  Layer. — The  m.  abductor  hallucis  arises  from  the  medial 
surface  of  the  tuberosity  of  the  calcaneus,  from  the  lig.  laciniatum 
(internalannularlig.),  the  plantar  aponeurosis  and  intermuscular  sep- 
tum. It  is  inserted  into  the  medial  side  of  the  first  phalanx  of  the 
great  toe. 

Actions. — Flexes  and  abducts  the  great  toe. 

Nerve  Supply. — Medial  plantar  nerve  (L.  4,  5,  S.  1). 

The  m.  flexor  digitorum  brevis  arises  from  the  ventral  part  of  the 
medial  process  of  the  tuberosity  of  the  calcaneus  and  from  the  central 
plantar  aponeurosis  and  intermuscular  septa.  It  is  inserted  by  four 
tendons  into  the  sides  of  the  second  phalanges  of  the  four  lesser 
toes.  Each  tendon  splits  to  permit  the  corresponding  tendon  of  the 
m.  flexor  digitorum  longus  to  pass  through. 

Actions. — Flexes  the  toes. 

Nerve  Supply. — Medial  plantar  nerve  (L.  4,  5,  S.  1). 

The  m.  abductor  digiti  quinti  arises  from  the  tuberosity  of  the  cal- 
caneus, from  the  lateral  part  of  the  plantar  aponeurosis  and  inter- 
muscular septum.  It  is  inserted  into  the  lateral  surface  of  the  base 
of  the  first  phalanx  of  the  little  toe. 

Actions. — Flexes  and  abducts  the  little  toe. 


208  MYOLOGY 

Nerve  Supply. — Lateral  plantar  nerve  (S.  i,  2). 

Second  Layer. — The  mm.  lumbricales  are  jour  muscles  associated 
with  the  flexor  digitorum  longus  tendons.  The  first  arises  from  the 
medial  side  of  the  tendon  for  the  second  toe  and  the  others  arise  from 
the  adjacent  side  of  all  four  tendons.  Each  muscle  is  inserted  into 
the  extensor  tendon  and  the  base  of  the  first  phalanx  of  the  four 
outer  toes,  as  in  the  hand. 

Actions. — Flex  the  metatarsophalangeal  joints  and  extend  the 
interphalangeal  joints  of  the  four  outer  toes. 

Nerve  Supply. — The  first  or  medial  lumbricale,  medial  plantar 
nerve  (L.  4,  5,  S.  1);  the  other  three,  lateral  plantar  nerve  (S.  1,  3). 


Pig.  161. — The  plantar  aponeurosis 
(Sobotta  and  McMvrrich.) 


Fig.  162. — -The  superficial  layer 
of  the  plantar  muscles.  The  plantar 
fascia  has  been  largely  removed  from 
the  surface  of  the  flexor  digitorum 
brevis.     (Sobotta  and  McMurrkh.) 


The  m.  quadratus  plantae  or  accessorius,  arises  from  the  lateral 
margin  of  the  plantar  ligament  and  the  adjacent  portion  of  the  plan- 
tar surface  of  the  calcaneus;  a  medial  head  arises  from  the  medial 
margin  of  the  long  plantar  ligament  and  from  the  medial  surface  of 
the  calcaneus.  Its  flattened  tendon  is  inserted  into  the  tendons  of 
the  flexor  digitorum  longus  (mainly  for  the  second,  third  and  fourth 
toes) . 

Actions. — Assists  in  flexing  the  toes  and  draws  the  long  tendons 
into  the  middle  of  the  sole  of  the  foot. 

Nerve  Supply. — Lateral  plantar  nerve  (S.  1,  2). 

The  tendons  of  the  mm.  flexor  hallucis  longus  and  flexor  digitorum 
longus  are  included  in  this  layer. 

Third  Layer. — The  m.  flexor  hallucis  brevis  arises  from  the  tendon 


THE  MUSCLES  OF  THE  FOOT 


209 


of  the  tibialis  posterior  and  the  plantar  surface  of  the  cuboid  bone. 
It  forms  two  tendons  (between  which  the  tendon  of  the  m.  flexor 
hallucis  longus  passes)  which  are  inserted  into  the  medial  and  lateral 
surfaces  of  the  base  of  the  first  phalanx  of  the  great  toe,  blending  with 
the  other  tendons  inserted  here. 

Action. — Flexes  the  great  toe  at  the  metatarsophalangeal  joint. 

Nerve  Supply. — Medial  plantar  nerve  (L.  4,  5,  S.  1). 

The  m.  adductor  hallucis  arises  by  two  heads.  The  oblique  head 
arises  from  the  plantar  surfaces  of  the  second,  third  and  fourth  meta- 


Vaoinol  lip 


Tendons  of  flexor 
dio.  lohg. 

Adductor  dig.  1/ 
Interczset 
r/exor  dig.  V- 


Abduclor  did  V 
Fle*.or  dig.  bre\ 
Abductor  iiallucis  \ 


,.      f.     Abductor  did  V 
tibialis  post.     Flexor  d.fbre 
Tendon  of  flexor  Abductor  M/uc, 
hallucis  Ion dus 

of  plantar  mus- 
is,  the  abductor 


Tendon  of  abductor  ha/locisc 
Adductor  hallucis 
(oblique  head) 

Flexor  ha/luc/s 
bre/i's 


Tendon  off/exor 
'torum  londusX 


Tendon  of  flexor 
hallucis  IbniJusX 


Fie,  H)j.— The  middle  laj 
cles.  The  flexor  digitorum  b: 
hallucis,  and  the  abductor  digiti  quinti  havt 
been  removed;  the  tendon-sheaths  of  the  digit: 
and  of  the  peronasus  longus  have  been  opened 
(Sobotta  and  Mc Munich.) 


Fig.  164. — The  deep  layer  of  plantar  muscles. 
The  tendons  of  the  flexor  digitorum  longus,  the 
flexor  hallucis  longus,  and  the  quadratus 
plantse  have  been  removed.  (Sobotta  and 
McMurrich.) 


tarsal  bones  and  from  the  sheath  of  the  m.  peroneus  longus  and  is 
inserted  into  the  lateral  surface  of  the  base  of  the  phalanx  of  the  great 
toe.  The  transverse  head  arises  from  the  transverse  metatarsal  liga- 
ments and  the  capsules  of  the  metatarsophalangeal  joints  (outer 
four).     It  is  inserted  with  the  oblique  head. 

Actions. — Adducts  and  flexes  the  great  toe. 

Nerve  Supply. — Lateral  plantar  nerve. 

The  m.  flexor  digiti  quinti  brevis  arises  from  the  base  of  the  fifth 
metatarsal  bone  and  the  sheath  of  the  m.  peroneus  longus.  It  is 
inserted  into  the  lateral  surface  of  the  base  of  the  first  phalanx  of  the 
little  toe. 

Action. — Flexes  the  little  toe. 

Nerve  Supply. — Lateral  plantar  nerve. 


Fourth  Layer. — The  mm.  interossei  are  seven  in  number,  four  dorsal 
and  three  plantar. 

The  dorsal  muscles  occupy  the  four  interosseous  spaces  and  each 
arises  from  the  adjacent  surfaces  of  two  metatarsal  bones.  The 
tendons  of  the  first  and  second  are  inserted  into  the  first  phalanx  of  the 
second  toe  (medial  and  lateral  surface).  The  third  and  fourth  are 
inserted  into  the  lateral  surfaces  of  the  first  phalanges  of  the  third 
and  fourth  toes. 

The  three  plantar  interossei  are  located  in  the  three  lateral  spaces. 
Each  arises  from  the  medial  surface  of  the  third,  fourth  and  fifth 
metatarsal  bones  and  is  inserted  into  the  medial  surface  of  the  first 
phalanges  of  the  third,  fourth  and  fifth  toes. 

Actions. — Flex  the  metatarsophalangeal  joints  and  extend  the  in- 
terphalangeal  joints. 

The  plantar  interossei  adduct  the  toes  toward  the  second  toe;  the 
dorsal  interossei  abduct  their  respective  toes  from  the  middle  line 
of  the  second  toe. 

Nerve  Supply. — Lateral  plantar  nerve  (S.  1,2). 


CHAPTER  IV 

THE  BLOOD-VASCULAR  SYSTEM 

The  chief  organs  found  in  the  thorax  are  the  heart  with  its  peri- 
cardium and  the  great  vessels  as  the  aorta,  pulmonary  arteries,  in- 
nominate, left  common  carotid  and  subclavian  arteries,  the  innom- 
inate veins  and  the  superior  and  inferior  venae  cavae;  the  lungs  and 
pleurae;  the  esophagus,  trachea  and  bronchi;  the  vagal,  phrenic  and 
sympathetic  nerves,  the  thoracic  duct  and  part  of  the  thymus  body. 

In  order  to  comprehend  that  an  organ  is  enlarged  or  displaced  it  is 
necessary  to  know  its  normal  size,  position  and  outline  upon  the 
body  wall.  In  order  to  facilitate  physical  diagnosis  certain  lines 
are  drawn  upon  the  body  and  these  bound  certain  definite  regions. 
Bony  landmarks  are  used  wherever  possible.  The  various  lines  and 
regions  of  the  thorax  will  be  first  considered. 

Lines  of  the  Thorax. — For  the  convenience  of  outlining  the  organs 
upon  the  body  surface,  a  number  of  vertical  and  transverse  lines 
are  drawn.  The  chief  vertical  lines  are  the  midst ernal,  midclavicular, 
lateral  sternal,  parasternal,  midaxillary,  scapidar  and  midverlebral. 

The  midsternal  line  (one)  is  drawn  from  the  midsternal  notch 
and  if  continued  upon  the  abdominal  wall  would  pass  through  the 
umbilicus  and  symphysis  pubis. 

The  midclavicular  lines  (two)  are  drawn  from  the  middle  of  the 
clavicle  through  the  nipple  of  the  male  and  if  continued  upon  the 
abdomen  would  pass  through  the  middle  of  the  inguinal  ligament. 

The  lateral  sternal  lines  are  two  lines  at  the  right  and  left  borders 
of  the  sternum. 

The  parasternal  lines  are  two  vertical  lines  midway  between  the 
midsternal  and  midclavicular  lines.  Some  place  these  lines  midway 
between  the  lateral  sternal  and  the  midclavicular  lines. 

The  midaxillary  lines  (two)  are  drawn  from  the  apex  of  the  axilla 
(armpit)  with  the  arms  extended  at  a  right  angle  to  the  body. 

The  scapular  lines  (two)  are  drawn  vertically  through  the  inferior 
angle  of  each  scapula. 

The  midverlebral  line  (one)  is  drawn  along  the  spinous  processes 
of  the  thoracic  vertebrae. 

The  horizontal  lines  upon  the  ventral  surface  are  as  follows: 

i.  At  the  lower  border  of  the  cricoid  cartilage. 

2.  Through  the  clavicles. 


CHE    BLOOD-VASCULAR    SYSTEM 


3.  Through  the  third  chondrosternal  junction. 

4.  Through  the  sixth  chondrosternal  junction. 

With  the  two  lines  at  the  sternal  borders  the  following  regions  are 
outlined: 

I.  Suprasternal,  containing  the  trachea,  thyreoid  gland  and  the 
esophagus. 


Fig.  165. — Lines  and  regions  of  the 
ventral  thoracic  and  abdominal  walls. 
{From  a  Photograph.)  a,  Midsternal; 
b,  b,  parasternal;  c,  (-.midclavicularlines; 
e,  subcostal  line;  /,  intertubercular  lines; 
g,  subcostal  angle;  hd,  ltd,  midinguinal 
lines.  RL  right  and  left  hypochondriac 
regions;  RL,  LL,  right  and  left  lumbar 
regions;  RI,  LI,  right  and  left  inguinal 
regions;  E,  epigastric;  U,  umbilical;  H 
hypogastric  regions;  M,  McBurney's 
point. 


Fig.  166. — Outline  of  regions  on  the 
ventral  thoracic  wall.  {From  a  Photo- 
graph.) a.  Line  through  cricoid  cartilage; 
b,  line  through  clavicles;  c.  line  through 
third  chondrosternal  articulation;  d,  line 
through  sixth  chondrosternal  articula- 
tion; e,  e  lateral  sternal  lines;  /,  angle  of 
Ludovicius.  1,  Suprasternal  region;  2,2, 
supraclavicular  regions;  3,  upper  sternal 
region;  4,  4,  infraclavicular  regions;  5, 
lower  sternal  region;  6,  6.  mammary 
regions;  7,  7,  inframammary  regions. 


2,  2.  The  supraclavicular  regions  containing  the  apex  of  each  lung 
and  the  cervical  pleura. 

3,  Upper  sternal  region  containing  the  thymus,  the  arch  of  the 
aorta  and  the  medial  border  of  the  upper  border  of  each  lung. 

4,  4.  The  infraclavicular  regions  containing  the  upper  lobe  of  each 
lung  where  tuberculous  bronchopneumonia  is  first  manifested. 

5,  Lower  sternal  region  containing  the  ventral  border  of  the  right 
lung  and  the  uncovered  area  of  the  heart. 

6,  6.  The  mammary  regions  containing  the  bulk  of  the  lungs  and 
the  bulk  of  the  heart. 


LINES    OF   THE    THORAX 


213 


7,  7.  The  inframammary  regions  containing  the  lower  portions  of  the 
lungs  and  the  costophrenic  sinuses.  These  regions  overlap  the  right 
lobe  of  the  liver  upon  the  right  side  and  on  the  left  side  the  left  lobe 
of  the  liver,  the  fundus  of  the  stomach  and  the  spleen.  Upon  the 
left  is  Traube's  semilunar  space. 

The  horizontal  lines  upon  the  dorsal  surface  are  as  follow 

1.  At  the  upper  borders  of  the  scapulae. 

2.  Through  the  spines  of  the  scapulae. 

3.  Through  the  inferior  angles  of  the  scapulas. 


Fig.  167. — Lines  and  regions  on  the  dorsal  thoracic  wall.  a.  Midvertebral  line;  b,  b.  scapu- 
lar lines  prolonged  headward;  c,  a  line  at  the  upper  borders  of  the  scapula?;  d.  a  line  through 
the  spines  (bases)  of  the  scapula?;  e,  a  line  at  the  apex  of  the  inferior  angles  of  the  scapula?. 
1,1,  Suprascapular  regions;  2,  2,  supraspinous  regions;  3,3,  infraspinous  regions;  4,  4,  inter- 


scapular regions;  5,  5,  infrascapular  regions.     (Fn 


■  photograph.) 


In  conjunction  with  the  midvertebral  and  the  scapular  lines  pro- 
longed upward  to  the  shoulder  the  following  regions  are  outlined: 

1,  1.  Scapular  regions. 

2,  2.  Supraspinous  regions. 
7,,  7,.  Infraspinous  regions. 

4,  4.  Interscapular  regions. 

5,  5.  Infrascapular  regions. 

Occupying  the  bulk  of  each  side  of  the  thoracic  cavity  are  seen 
the  lung  and  pleural  membranes.  The  region  between  the  two 
pleural  sacs  is  called  the  interpleural  space,  or  septum  mediastinale. 
This  region  is  not  a  space  in  the  true  sense  as  it  is  occupied  by  various 
organs  and  structures. 


214 


THE  BLOOD-VASCULAR   SYSTEM 


The  mediastinal  septum  is  divided  into  two  main  portions,  supe- 
rior and  inferior.  The  superior  mediastinum  lies  above  the  level  of 
the  pericardium,  extending  from  the  junction  of  the  manubrium  and 


Fig.    169. — The  ventral,  middle  and  dorsal  mediastinal  spaces  (at  the  level  of  the  disc 
between  ninth  and  tenth  thoracic  vertebrae). 

gladiolus  sterni  to  the  lower  border  of  the  fourth  thoracic  vertebra. 
In  this  region  lie  the  arch  of  the  aorta  and  its  three  branches,  the 
upper  part  of  the  superior  vena  cava  and  the  innominate  veins,  the 
esophagus,  trachea,  thoracic  duct,  the  vagal,  phrenic,  cardiac,  re- 
current laryngeal  and  sympathetic  nerves  and  the  thymus  gland. 


THE    HEART 


215 


The  inferior  mediastinum  is  the  widest  portion  and  is  divided  into 
ventral,  middle  and  dorsal  portions.  The  ventral  lies  between  the 
sternum  and  the  pericardium  and  contains  some  lymph  nodes, 
branches  of  the  internal  mammary  artery  and  areolar  tissue. 

The  middle  portion  is  the  largest  and  is  bounded  by  the  pericar- 
dium. Its  contents  are  the  pericardium,  heart,  roots  of  the  great 
vessels  and  the  phrenic  nerves. 

The  dorsal  mediastinum  lies  behind  the  pericardium.  Its  contents 
are  the  descending  thoracic  aorta,  the  thoracic  duct,  vena  azygos 
major,  vagal  nerves  and  esophagus. 

The  blood  vascular  system  consists  of  the  heart,  arteries,  that  carry 
the  blood  away  from  the  heart,  veins,  that  carry  the  blood  toward  the 
heart  and  capillaries  that  connect  the  arteries  and  veins.  There  are 
two  main  circulations,  the  systemic  and  the  pulmonary.  The  systemic 
is  farther  divided  into  the  general  systemic  and  the  portal  circulations. 


Fig.  170. — Ventral 


of   the  heart.      (From  a  photograph.) 


THE  HEART 


The  heart  (cor)  is  a  hollow  muscular  organ  of  a  flattened,  conical 
shape  situated  in  the  thoracic  cavity.  It  is  contained  in  a  serous 
sac  called  the  pericardium.  About  one-third  lies  to  the  right  of  the 
midsternal  line  and  two-thirds  to  the  left.  Its  long  axis  is  directed 
downward  (caudad)  to  the  left  and  forward  (ventrad).     Its  dimen- 


2l6  THE    BLOOD-VASCULAR    SYSTEM 

sions  are  5  inches  (12.5  cm.)  long,  3.5  inches  (8.75  cm.)  wide  and  2.5 
inches  (6.25  cm.)  thick.  It  weighs  10  to  12  ounces  in  the  male  and 
8  to  10  ounces  in  the  female. 

It  presents  a  base,  an  apex,  two  surfaces  and  two  margins.  The 
base  (basis  cordis)  is  directed  upward  (cephalad)  and  backward 
(dorsad)  and  is  formed  by  the  atria,  chiefly  the  left.  It  lies  ventral 
to  the  bodies  of  the  fifth,  sixth,  seventh  and  eighth  thoracic  vertebrae 
but  separated  from  them,  mainly,  by  the  esophagus  and  the  thoracic 
aorta.  It  presents  the  openings  of  the  pulmonary  veins  and  the 
superior  and  inferior  venae  cava;,  the  oblique  vein  and  fold  of  Marshal. 


Ate  fc»* , 


Fig.  171. — Dorsal  view  (base  and  diaphragmatic  surface)  of  the  heart.  The  vessels  are 
filled  with  cotton  to  make  them  stand  open.  (.From  a  photograph.)  L.P.A..  R.P.A..  Left  and 
right  pulmonary  arteries;  P.\'..  pulmonary  veins;  V.A.M.,  venaazygos  major.  P.I.G.,  dorsal 
(inferior)  interventricular  sulcus. 

The  base  is  limited  below  by  the  atrioventricular  groove  which  con- 
tains the  coronary  sinus. 

The  apex  (apex  cordis)  is  blunt  and  rounded  representing  the  left 
ventricle;  it  is  situated  in  the  fifth  left  intercostal  space  8  cm.  from 
the  midline. 

The  sternocostal  surface  (facies  sternocostal  is)  looks  upward 
(cephalad)  and  forward  (ventrad)  and  to  the  left.  It  lies  dorsal  to 
the  sternum  and  the  third,  fourth,  fifth  and  sixth  costal  cartilages, 
mainly  of  the  left  side.     The  upper  part  consists  of  the  two  atria  and 


THE  CHAMBERS  OF  THE  HEART  21 7 

roots  of  the  pulmonary  artery  and  aorta.  The  greater  part  of  the 
surface  consists  of  the  ventricles  separated  incompletely  from  the 
preceding  by  the  ventral  atrioventricular  groove.  This  ventricular 
area  is  convex  and  is  divided  into  a  larger,  right,  and  smaller,  left, 
portion  by  the  ventral  (superior)  interventricular  sulcus  which  goes  to 
the  right  of  the  apex. 

The  diaphragmatic  surface  (fades  diaphragmatica)  is  flattened  and 
rests  chiefly  upon  the  central  tendon  of  the  diaphragm.  It  consists 
of  the  ventricles  and  is  divided  into  a  greater,  left  ventricle,  and 
smaller,  right  ventricle  portions  by  the  dorsal  interventricular  sulcus. 

The  right  margin  consists  of  a  vertical  and  a  horizontal  portion. 
The  vertical  part  is  curved  and  is  formed  by  the  right  atrium;  it  is 
marked  by  the  sulcus  tcrminalis.  The  horizontal  portion  is  thin  and 
sharp  and  is  formed  by  the  right  ventricle;  this  latter  part  is  called 
also  the  inferior  margin,  or  margo  acutus. 

The  left  margin  is  convex  and  is  formed  mainly  by  the  left  ventri- 
cle. It  is  rounded  and  is  called  the  margo  obtusus.  It  is  obliquelv 
directed  with  its  convexity  to  the  left. 

The  chambers  of  the  heart  are  four  in  number:  right  and  left  atria 
and  right  and  left  ventriculi.  The  right  atrium  communicates  with 
the  right  ventriculus  and  the  left  atrium  with  the  left  ventriculus. 
The  capacity  of  each  ventricle  is  about  100  c.c.  and  that  of  each 
atrium  slightly  less. 

Right  Atrium. — Make  an  incision  with  the  scissors  connecting  the  inferior  and 
superior  cava?;  from  the  middle  of  this  incision  make  another  into  the  auricular 
appendage.  By  these  incisions  the  atrium  is  laid  open  and  the  various  points 
of  interest  may  be  readily  examined. 

Right  Ventricle. — From  the  right  atrium  cut  into  the  right  ventricle  along  the 
inferior  margin  of  the  chamber  to  the  apex.  From  the  middle  of  this  incision 
carry  another  to  the  interventricular  groove  and  follow  the  interventricular 
septum  into  the  pulmonary  artery. 

Left  Atrium. — Make  an  incision  connecting  the  right  and  left  superior  pul- 
monary veins;  make  another  from  the  left  superior  pulmonary  vein  into  the 
appendage. 

Left  Ventricle. — Make  an  incision  from  the  left  atrium  into  the  left  ventricle 
following  the  left  border  of  the  heart  to  the  apex;  then  continue  along  the  in- 
terventricular sulcus  into  the  aorta  using  a  finger  of  the  left  hand  as  a  guide  to 
the  scissors. 

The  right  atrium  (atrium  dextrum)  consists  of  the  main  chamber 
and  the  auricle  (auricula  dextra).  The  points  of  interest  in  the 
interior  are  as  follows: 

1.  Crista  tcrminalis,  a  ridge  running  from  in  front  (ventral  margin) 
of  the  superior  vena  cava  to  in  front  of  the  inferior  vena  cava.  This 
ridge  is  marked  externally  by  a  groove,  the  sulcus  tcrminalis. 

2.  The  tricuspid  (right  atrioventricular)  orifice  leading  into  the 
right  ventricle. 


2l8  THE   BLOOD-VASCULAR    SYSTEM 

3.  The  orifice  of  the  superior  vena  cava  at  the  upper  (cephalad)  and 
back  (dorsal)  part  of  the  atrium. 

4.  The  orifice  of  the  inferior  vena  cava  at  the  lowest  part  of  the 
atrium. 

5.  The  Eustachian  valve  {valvida  vena  cava  inferioris)  situated  in 
front  of  (ventral  to)  the  orifice  of  the  inferior  vena  cava  and  extend- 
ing to  the  fossa  ovalis. 

6.  The  coronary  sinus  (sinus  coronarius)  opening  between  the 
orifice  of  the  inferior  vena  cava  and  the  tricuspid  orifice. 

7.  The  coronary  valve  (valvula  sinus  coro-narii)  that  protects  the 
orifice  of  the  coronary  sinus. 

8.  Foramina  thebesii  (vena  cordis  minima)  openings  of  small  veins 
in  the  walls  of  the  atrium. 

9.  Fossa  ovalis,  a  depression  in  the  lower  part  of  the  interatrial 
septum. 

10.  Annulus  ovalis  (limbus  fossa  ovalis)  the  incomplete  ridge  form- 
ing the  boundary  of  the  fossa  ovalis. 

n.  The  musculi  pectinati,  the  muscle  columns  in  the  auricle. 

12.  The  openings  of  the  anterior  cardiac  veins  at  the  lower  part  of 
the  front  (ventral)  wall  of  the  atrium. 

13.  The  tubercle  of  Lower  (tuberadum  intervenosum)  a  small  pro- 
jection between  the  fossa  ovalis  and  the  superior  and  inferior  venae 
cavae,  not  prominent  in  man. 

The  right  ventricle  (ventricuhts  dexter)  is  pyramidal  in  form  and  the 
cavity  consists  of  the  main  part,  or  body,  and  the  conus  arteriosus, 
that  leads  into  the  pulmonary  artery.  These  two  parts  are  separated 
by  a  slight  ridge,  the  supraventricularcrest.  The  walls  in  the  body 
portion  are  thinner  than  those  of  the  left  ventricle  and  are  irregular, 
due  to  the  presence  of  the  trabecula  cornea.  The  walls  of  the  conus 
arteriosus  are  smooth.     The  points  of  interest  are  as  follows: 

1.  The  tricuspid  orifice  communicating  with  the  right  atrium, 
guarded  by  the  tricuspid  valve.  It  is  oval  and  is  directed  obliquely 
downward  (caudad)  and  to  the  right. 

2.  The  pulmonary  artery  orifice  at  the  upper  (cephalic)  and  front 
(ventral)  part  of  the  chamber  and  at  the  end  of  the  conus  arteriosus. 

3.  Vena  cordis  minima,  the  openings  of  small  veins  in  the  walls. 

4.  Trabecula  carnea,  or  muscle  columns  of  three  varieties,  ridges, 
arches  and  papillary  muscles.  The  last,  musculi  papillares,  are  more 
or  less  massive  projections  attached  to  the  ventricular  wall  by  their 
bases.  The  papillary  muscles  usually  number  three:  (1)  a  large 
ventral,  (2)  a  smaller  dorsal,  (3)  a  single,  or  group  of  papilla;  (septal) 
attached  to  the  interventricular  septum.  To  the  summit  of  each  are 
attached  the  chordae  tendineas. 

5.  The  moderator  band,  a  modified  column  attached  at  one  end  to 
the  interventricular  septum  and  at  the  other  to  the  base  of  the  ventral 


THE  CHAMBERS  OF  THE  HEART 


219 


papillary  muscle.     It  tends  to  prevent  over-distention  of  the  ven- 
tricle and  is  prominent  in  lower  animals. 

6.  The  tricuspid  valve  (valvule  trims pidalis)  consists  of  three  some- 
what triangular  leaflets.  The  base  of  each  is  attached  to  the  atrio- 
ventricular orifice  and  the  free  edges  are  serrated;  from  the  serrations 
delicate  tendinous  threads,  the  chorda  tendinea,  pass  to  the  papillary 
muscles.  The  left,  or  infundibular  cusp,  is  the  largest  and  is  situated 
over  the  conus  arteriosus.  The  right,  or  marginal  cusp,  is  in  rela- 
tion with  the  right  part  of  the  ventral  wall;  the  medial,  or  septal  cusp, 


— Heart  dissected 
entricle.     A,  Chordae  tend 


B,  eustachian  valve;  C.  coronary  vaK 


and  the  right 


is  in  relation  with  the  interventricular  septum.  This  valve  guards 
the  atrioventricular  orifice. 

7.  The  chorda;  tendineaz  are  delicate  cords  that  attach  the  valve 
edges  and  central  parts  of  the  valve  leaflets  to  the  papillary  muscles 
and  prevent  the  leaflets  from  passing  into  the  atrium. 

The  left  atrium  (atrium  sinistrum)  consists  of  the  body  and  the 
auricle.  The  body  is  smooth-walled  while  the  auricular  wall  is 
roughened.     The  points  of  interest  are  as  follows: 

1.  Orifice  of  the  four  pulmonaxy  veins  opening  into  the  upper 
(cephalic)  part  of  the  dorsal  wall. 


220  THE    BLOOD-VASCULAR    SYSTEM 

2.  The  atrioventricular  orifice  communicating  with  left  ventricle. 

3.  Vena  cordis  minima. 

4.  Musculi  pectinati  in  the  auricula. 

The  left  ventricle  (ventriculus  sinister)  has  thicker  walls  than  the 
right  ventricle  (3  to  1)  and  is  somewhat  cylindrical  in  form.  The 
cavity  is  divided  into  body  (irregular  wall)  and  vestibule  (smooth- 
walled)  that  leads  to  the  aorta.  The  points  of  interest  are  as 
follows: 

1.  Bicuspid  orifice  that  communicates  with  the  left  atrium  and  is 
guarded  by  the  bicuspid  valve. 

2.  The  aortic  orifi.ce  that  leads  into  the  aorta  and  is  situated  at  the 
upper,  front  part  at  the  summit  of  the  vestibule.  It  is  circular  in 
outline  and  lies  ventral  to  the  preceding  orifice. 

3.  Vena  cordis  minima. 

4.  Trabecula  cornea:  ridges,  arches  and  papillary  muscles.  The 
papillary  muscles  (musculi  papillares)  are  two  in  number,  ventral  and 
dorsal,  or  inferior  and  they  are  much  larger  than  those  of  the  right 
ventricle.     To  these  the  chorda;  tendinea;  are  attached. 

5.  The  bicuspid  valve  (valvula  mitralis)  consists  of  two  leaflets,  the 
ventral,  or  aortic  cusp  is  the  larger,  the  inferior,  or  marginal  cusp  is 
the  smaller.  Usually  two  smaller  cusps  are  found  at  the  angles  of 
junction  of  the  larger  cusps.  The  free  edges  of  the  leaflets  are  ser- 
rated and  have  the  chordae  tendinea;  attached  here  as  well  as  to  the 
under  surfaces  of  the  valve  leaflets. 

6.  The  chorda  tendinea  are  attached  like  those  of  the  right  ven- 
tricle but  are  thicker  and  stronger. 

The  interventricular  septum  (septum  ventriculorum)  separates  the 
two  ventricles.  It  corresponds  to  the  interventricular  sulcus  and  has 
an  oblique  position.  The  bulk  of  it  consists  of  muscle  tissue,  the 
upper  (cephalic)  and  ventral  part  in  membranous  and  is,  therefore, 
called  the  pars  membranacea. 

The  muscle  tissue  of  the  heart  is  arranged  differently  in  the  atria 
than  in  the  ventricles.  In  the  atria  two  layers  are  noted.  The 
superficial  layer  runs  transversely  and  is  common  to  both  chambers. 
The  deep  layer  consists  of  fibers  that  loop  over  each  atrium  from  front 
to  back  (dorsoventrally)  and  form  circular  bands  around  the  auricula; 
and  orifices  of  the  veins.  In  the  ventricles  the  arrangement  is  more 
complex.  The  superficial  set  consists  of  fibers  that  arise  from  the 
conus  arteriosus  and  pass  across  the  right  ventricle  around  the  apex 
and  thence  to  the  papillary  muscles  of  the  left  ventricle.  Other 
fibers  arise  from  the  right  atrioventricular  ring,  pass  beneath  the 
preceding,  around  the  apex  to  the  dorsal  papillary  muscle  of  the  left 
ventricle.  Some  fibers  arise  from  the  left  atrioventricular  ring  and 
pass  to  the  right  ventricle  and  its  papillary  muscles.  The  deep  set 
(larger)  consists  of  fibers  that  arise  in  the  papillary  muscles  of  one 


THE    PERICARDIUM  221 

ventricle,  describe  an  S-shaped  course  and  pass  under  the  papillary 
muscles  of  the  other  ventricle.  There  are  three  sets  of  these  and 
the  course  is  very  complicated. 

The  atrioventricular  bundle  (His)  connects  the  right  atrium 
directly  with  the  ventricles.  This  bundle  of  muscle  fiber  arises  near 
the  fossa  ovalis  as  small  bundles  of  fibers  that  converge  to  form  its 
node;  it  then  continues  as  a  single  bundle  in  the  lower  part  of  the  pars 
membranacea  to  the  muscular  portion  of  the  interventricular  septum. 
Here  the  bundle  divides  into  right  and  left  portions  one  for  each 
ventricle.  Each  passes  down  its  respective  side  of  the  interventricu- 
lar septum,  beneath  the  endocardial  lining,  to  ultimately  divide 
to  numerous  bundles  that  pass  to  the  papillary  muscles  and  then 
spread  out  over  the  entire  ventricular  muscle. 

The  heart  receives  its  blood  supply  through  the  rigid  and  left 
coronary  arteries  that  arise  from  the  aorta  in  the  sinuses  of  Valsalva. 
The  blood  is  returned  to  the  right  atrium  through  the  coronary  sinus 
and  the  anterior  cardiac  veins.  The  tributaries  of  the  coronary 
sinus  are  the  small,  or  right  cardiac  vein  and  the  middle,  or  posterior 
cardiac  veins.  The  lymph  drains  into  the  right  lymphatic  and  thor- 
acic ducts. 

The  nerve  supply  is  from  the  vagal,  accessory  and  sympathetic 
nerves. 

The  pericardium  is  a  fibrous  sac  lined  by  a  serous  membrane.  It 
is  conical  in  shape  with  its  base  downward  (caudad)  and  apex  up- 
ward (cephalad).  The  base  is  attached  to  the  central  tendon  of  the 
diaphragm  while  the  apex  is  continuous  with  the  cervical  fascia. 
The  sac  contains  the  heart  and  the  cardiac  ends  of  the  great  vessels. 
Its  ventral  wall  gives  attachment  to  the  superior  and  inferior  sterno- 
pericardial ligaments.  It  constitutes  the  boundary  of  the  middle 
mediastinal  space  as  well  as  assists  in  bounding  the  ventral  and 
dorsal  mediastinal  spaces.  At  its  base  it  is  pierced  by  the  inferior 
vena  cava  and  at  its  apex  (dorsally)  it  is  pierced  by,  and  its  fibrous 
part  also  ensheaths  the  superior  vena  cava,  pulmonary  veins, 
right  and  left  pulmonary  arteries  and  aorta. 

The  serous  portion  consists  of  a  visceral  layer,  upon  the  heart,  and 
a  parietal  layer,  lining  the  fibrous  sac.  These  two  are  continuous 
over  the  great  vessels  of  the  heart  but  all  of  the  vessels  do  not  receive 
a  complete  investment.  As  a  result  recesses,  or  sinuses,  are  formed. 
The  great  transverse  sinus  lies  between  the  pulmonary  artery  and  the 
aorta  (ventrally)  and  the  two  atria  (dorsally).  The  great  oblique 
sinus  lies  between  the  inferior  vena  cava  (to  the  right  and  below) 
and  the  left  inferior  pulmonary  vein  (to  the  left  and  above). 

The  vestigial  fold  of  Marshall  is  a  fold  of  serous  pericardium  en- 
closing the  ligamcutum  vena  cava  sinistra.  It  passes  from  the  left 
pulmonary  artery  region  to  the  left  superior  pulmonary  vein. 


22  2  THE   BLOOD-VASCULAR    SYSTEM 

To  outline  the  heart  upon  the  ventral  thoracic  wall  the  following 
points  are  used:  (i)  3  cm.  from  the  midsternal  line  upon  the  upper 
margin  of  the  third  right  costal  cartilage;  (2)  2.5  cm.  from  the  mid- 
sternal  line  at  the  sixth  chondrosternal  junction;  (3)  8  cm.  from  the 
midsternal  line  in  the  left  fifth  interspace  (apex  point);  (4)  4.5  cm. 
from  the  midsternal  line  in  the  second  left  interspace.  The  line  1,  2 
should  be  curved  to  the  right  so  as  to  be  3.5  cm.  from  the  midsternal 
line  at  the  fourth  interspace.     This  line  represents  the  right  atrium. 


Fig.  173. — Outline  of  the  heart  upon  the  ventral  thoracic  wall.  {From  a  photograph . 
P,  Pulmonary  valve;  A,  aortic  valve;  M,  mitral  valve;  T  tricuspid  valve,  i,  2,  3,  4,  point 
for  outlining  the  heart. 


The  line  2,  3  represents  the  right  ventricle.  The  line  3,  4  should  be 
curved  a  little  to  the  left  and  represents  the  left  border  and  mainly 
left  ventricle.  The  line  1,  4  represents  the  base  line.  The  valves 
are  located  as  follows:  The  pulmonary  valve  is  placed  horizontally 
beneath  the  middle  of  the  third  left  chondrosternal  junction.  The 
aortic  valve  is  below  this  and  toward  the  midline  and  at  an  angle. 
The  mitral  valve  is  opposite  the  third  left  interspace  and  nearly 
horizontal,  while  the  tricuspid  valve  is  below  this  near  the  midline 
and  at  an  angle,  slightly  overlapping  the  mitral  valve.  These  areas 
indicate  the  position  of  the  valves  but  do  not  indicate  the  regions 
where  the  valve  sounds  are  best  heard.  These  latter  are  called  the 
puncta  maxima  and  are  as  follows: 


THE    ARTERIES 


223 


i.  Pulmonary  punctum  maximum  (p.  m.)  is  at  the  sternal  end  of 
the  second  left  intercostal  space. 

2.  Aortic  p.  m.  is  at  the  second  right  costal  cartilage. 

3.  Mitral  p.  m.  is  just  above  the  area  of  the  apex  point. 

4.  Tricuspid  p.  m.  is  at  the  sternal  ends  of  the  fifth  and  sixth 
costal  cartilages. 

That  portion  of  the  heart  that  lies  immediately  beneath  the  ven- 
tral thoracic  wall  and  separated  from  it  by-  only  the  pericardium  and 


Fig.  174. — Diagram  of  the  heart  and  valves  in  relation  to  the  skeleton  of  the  ventral 
thoracic  wall.  PC,  Superior  vena  cava;  RA,  right  atrium;  RV,  right  ventricle;  LA,  left 
atrium;  LV,  left  ventricle;  P,  pulmonary  valve;  A,  aortic  valve;  M,  mitral  valve;  T,  tri- 
cuspid valve. 

pleurae  is  called  the  area  of  superficial  cardiac  dulness  and  is  chiefly 
ventricular;  the  remainder  is  overlapped  by  the  lungs  and  gives  the 
deep  cardiac  dulness. 

THE  ARTERIES 

The  circulations  are  the  pulmonary  and  systemic;  the  systemic  is 
divided  into  general  systemic  and  portal. 

The  pulmonary  circulation  comprises  the  right  ventricle,  the  pul- 
monary aorta  and  the  pulmonary  arteries,  the  lungs,  pulmonary 
veins  and  the  left  atrium. 


224 


THE    BLOOD-VASCULAR    SYSTEM 


The  pulmonary  aorta,  or  artery  (artcria  pulmonalis) ,  leaves  the 
right  ventricle  at  the  summit  of  the  conus  arteriosus.  The  vessel 
is  about  2  inches  (5  cm.)  long  and  1  ii  inches  (30  mm.)  in  diameter. 
It  passes  upward  (cephalad)  and  dorsally  and  under  the  arch  of  the 
aorta  it  divides  into  right  and  left  pulmonary  arteries  which  further 
divide  and  ramify  the  lungs.  The  base  of  the  pulmonary  aorta 
has  three  dilatations  called  the  sinuses  of  Valsalva,  two  ventral  and 
one  dorsal.  Here  are  seen  the  semilunar  valves,  three  in  number; 
each  valve  is  semilunar  in  shape  and  is  attached  by  its  peripheral 


1     -RCm.CMrt,  IMjIV0'1* 


Lisflrt 


ch  of  the  aorta  and  its  branches;  the  superior  ' 
the  pulmonary  arteries  and  vein: 


.  and  its  tributaries; 


margin  to  the  base  of  the  pulmonary  artery  (annul  us  Jibrosus) .  The 
inner,  or  free  edge,  near  its  middle  possesses  a  nodule  called  the 
cor  pits  aranlii  (modulus  valvules  semilunaris).  From  each  side  of  this 
a  minute  semilunar  fold  extends  and  is  called  lunule  (lunula).  The 
right  pulmonary  artery  is  larger  and  longer  than  the  left.  Its  first 
branch  lies  below  the  first  branch  bronchus.  The  first  branch  of 
the  left  pulmonary  artery  passes  above  the  first  branch  bronchus. 

The  pulmonary  veins  (vena  pulmonales)  are  four  in  number.  The 
lobular  divisions  unite  to  form  one  vein  for  each  lobe,  three  in  the 
right  lung  and  two  in  the  left  lung.  The  middle  vessel  on  the  right 
side  joins  that  of  the  upper  lobe  so  that  two  veins  leave  each  lung 
to  empty  into  the  left  atrium.     No  valves  are  present. 

In  the  pulmonary  circulation   the  venous  or  deoxygenated  blood 


THE  ARTERIES  OF  THE  HEAD  AND  NECK         225 

passes  from  the  right  ventricle  into  the  pulmonary  artery,  through 
its  right  and  left  branches  to  the  lungs  where  it  is  oxygenated  in  the 
capillaries.  The  blood  then  continues  into  the  radicals  of  the  pul- 
monary veins  and  through  these  veins  to  the  left  atrium. 

The  systemic  circulation  is  more  extensive  and  more  complicated; 
it  comprises  the  left  ventricle,  the  aorta  and  its  branches,  the  sys- 
temic capillaries,  the  superior  and  inferior  venae  cavae  and  their 
tributaries  and  the  right  atrium. 

The  aorta  consists  of  an  ascending  portion,  arch  and  descending 
portion;  the  last  is  divided  into  thoracic  and  abdominal  parts. 

The  ascending  portion  (aorta  ascendens)  arises  from  the  summit 
of  the  vestibule  of  the  left  ventricle.  It  is  about  2  inches  (5  cm.) 
in  length  and  i'6  inches  (28  mm.)  in  diameter.  At  its  root  (bulb us 
aorta)  it  possesses  three  dilatations,  the  sinuses  of  Valsalva,  two 
dorsal  and  one  ventral.  Here  are  seen  the  semilunar  valves  and 
these  are  the  same  in  structure  as  those  of  the  pulmonary  artery. 
From  the  ventral  sinus  arises  the  right  coronary  artery  and  from  the 
left  dorsal  sinus  arises  the  left  coronary  artery.  These  arteries  nour- 
ish the  heart. 

The  ascending  aorta  passes  obliquely  upward  (cephalad),  ventrally 
and  to  the  right,  to  the  level  of  the  upper  border  of  the  second  right 
costal  cartilage.  Here  the  arched  part  (arcus  aorta)  continues  up- 
ward (cephalad),  dorsally  and  to  the  left  across  the  trachea  and 
thence  downward  (caudad)  to  the  level  of  the  lower  border  of  the 
fourth  thoracic  vertebra;  here  it  constitutes  the  beginning  of  the 
descending  aorta.  The  arch  has  three  branches,  the  innominate,  left 
common  carotid,  and  left  subclavian  arteries. 

The  innominate  artery  (arteria  innomyna)  is  the  largest  branch 
.of  the  aorta  and  measures  i'2  to  2  inches  (3.5  to  5  cm.)  in  length. 
It  lies  in  the  posterior  mediastinum  and  extends  to  the  root  of  the 
neck,  where  it  divides  into  the  right  common  carotid  and  right 
subclavian  arteries. 

THE  ARTERIES  OF  THE  HEAD  AND  NECK 

The  right  common  carotid  (arteria  carotid  is  communis  dexter) 
arises  in  the  root  of  the  neck  and  extends  to  the  upper  margin  of  the 
thyreoid  cartilage;  it  is  about  3'2  inches  (8.5  cm.)  in  length.  It  lies 
in  the  carotid  sheath  with  the  internal  jugular  vein  and  the  vagal 
nerve  and  divides  into  the  right  internal  and  external  carotid  arteries. 

The  left  common  carotid  artery  (arteria  carotidis  communis 
sinister)  arises  from  the  arch  of  the  aorta  and  extends  to  the  upper 
margin  of  the  thyreoid  cartilage.  It  consists  of  a  thoracic  and  a  cervi- 
cal portion.  The  thoracic  part  is  about  1  to  ili  inches  (2.5  to  3.5  cm.) 
in  length  and  extends  to  the  left  sternoclavicular  articulation.  The 
cervical  portion  starts  here  and  continues  as  on  the  right  side. 


2  26  THE   BLOOD-VASCULAR    SYSTEM 

The  course  of  either  common  carotid  artery  is  indicated  as  follows: 
Draw  a  line  from  the  sternal  end  of  the  clavicle  to  a  point  midway 
between  the  mastoid  process  and  the  angle  of  the  mandible.  That 
portion  of  the  line  inferior  to  the  upper  margin  of  the  thyreoid  car- 
tilage lies  over  the  artery. 

The  external  carotid  artery  (artcria  carotis  externa)  is  the  smaller 
of  the  two  branches  of  the  common  carotid  and  extends  from  the 
upper  margin  of  the  thyreoid  cartilage  to  the  back  of  the  neck  of  the 
mandible,  where  it  divides  into  the  internal  maxillary  and  super- 
ficial temporal  arteries.  It  is  about  2J2  inches  (6.1  cm.)  in  length. 
It  gives  off  the  following  branches: 

1.  The  superior  thyreoid  (art.  thyreoidea  superior)  is  the  first 
branch  and  arises  on  a  level  with  the  tip  of  the  greater  cornu  of  the 
hyoid  bone.  It  passes  to  the  superior  portion  of  the  thyreoid 
gland,  which  it  supplies,  and  in  addition  gives  branches  to  the  larynx 
and  sternomastoid  muscle. 

2.  The  lingual  artery  {artcria  lingua! is)  is  the  second  branch 
mainly  for  the  supply  of  the  tongue.  Its  chief  branches  are  the 
hyoid,  dorsal  lingual  and  sublingual  (for  the  sublingual  gland)  arteries. 

3.  The  external  maxillary,  or  facial  artery  (artcria  maxillaris 
externa)  arises  just  above  the  lingual  artery,  passes  up  the  neck,  over 
the  body  of  the  mandible  and  terminates  at  the  angle  of  the  mouth 
as  the  angular  artery.  In  the  neck  this  artery  gives  off  the  following 
arteries:  (a)  The  ascending  palatine,  for  the  soft  palate,  tonsil, 
pharynx  wall  and  the  auditory  tube,  (b)  The  tonsillar  artery,  for 
the  tonsil  and  constrictor  muscles  of  the  pharynx,  (c)  The  sub- 
maxillary artery,  for  the  submaxillary  gland,  (d)  The  submental 
artery,  for  the  submaxillary  and  sublingual  glands  and  the  mylohyoid 
muscle. 

In  the  face  the  following  branches  are  given  off:  (a)  The  superior 
labial,  or  coronary  artery,  that  supplies  the  upper  lip  and  part  of  the 
septum  of  the  nose,  (b)  The  masseteric  branch,  for  the  masseter 
muscle,  (c)  The  lateral  nasal  artery,  that  arises  near  the  angle  of 
the  mouth  and  supplies  the  ala  of  the  nose,  (d)  The  angular  artery 
is  the  terminal  part  of  the  external  maxillary  artery  and  runs  along 
the  side  of  the  nose  to  the  medial  commissure  of  the  eyelids. 

4.  The  occipital  artery  (art.  occipitalis)  arises  near  the  inferior 
margin  of  the  posterior  belly  of  the  digastric  muscle  and  extends  to 
the  inferior  nuchal  line  where  it  divides  into  its  terminal  branches. 
This  gives  off  a  number  of  branches,  (a)  Muscular  branches  to  the 
neighboring  muscles,  (b)  Meningeal  branches  that  enter  the  skull 
through  the  hypoglossal  canal  and  jugular  foramen  and  supply  the 
meninges  here,  (c)  The  descending  branch,  or  prince psccrvicis  artery, 
supplies  muscles  of  the  dorsal  vertebral  region.  ((/)  The  terminal 
branches  (medial  and  lateral)  supply  the  scalp  of  the  neighborhood. 


THE  ARTERIES  OF  THE  HEAD  AND  NECK 


227 


5.  The  posterior  auricular  artery  (art.  auricularis  posterior)  arises 
above  the  level  of  the  posterior  belly  of  the  digastric  muscle  and  ends 
back  of  the  auricle.  This  has  a  number  of  branches,  (a)  The 
muscular  branches  supply  the  sternomastoid,  digastric  and  styloid 
muscles,  (b)  The  parotid  branches  pass  to  the  parotid  gland,  (c) 
The  stylomastoid  artery  enters  the  stylomastoid  foramen  and  supplies 
the  external  auditory  canal,  the  tympanum,  vestibule,  semicircular 
canals  and  mastoid  cells,     (d)  The  auricular  branch  supplies  the 


-Ramification  of  the  external  carotid  artery  in  the  head  (diagrammatic). 
(Sobotta  and  McMurrich.) 


posterior  auricular  muscle,  the  auricle  and  scalp  of  the  region,  (e) 
The  occipital  branch  supplies  the  sternomastoid  and  occipitalis 
muscles  and  the  scalp  here. 

6.  The  ascending  pharyngeal  artery  (art.  pharyngea  ascendens) 
arises  from  the  lower  part  of  the  carotid  artery  and  passes  to  the 
pharynx  and  soft  palate.  Its  branches  are  as  follows:  (a)  Pharyn- 
geal branches  to  the  wall  of  the  pharynx  and  tonsil,  (b)  The  pre- 
vertebral branches  for  the  prevertebral  muscles,  deep  lymph  nodes  and 


228  THE    BLOOD-VASCULAK    SYSTEM 

large  nerves,  (c)  The  posterior  meningeal  for  the  meninges; 
these  enter  the  skull  through  the  hypoglossal  canal  and  jugular 
foramen.     (</)  The  inferior  tympanic  for  the  tympanum. 

7.  The  superficial  temporal  artery  (art.  temporalis  superficialis), 
one  of  the  terminal  branches  of  the  external  carotid  artery,  is  about 
1  to  2  inches  (2.5  to  5  cm.)  in  length.  Its  branches  are  numerous. 
(a)  Parotid  branches,  for  the  parotid  gland,  (b)  Articular,  for  the 
temporomandibular  articulation,  (c)  Anterior  auricular,  for  the 
auricle  and  external  auditory  canal,  (d)  Transverse  facial,  for  the 
parotid  gland  and  duct,  masseter  muscle  and  skin,  (e)  Middle 
temporal,  for  the  temporal  muscle.  (/)  The  zygomaticoorbital,  for 
the  orbicularis  oculi  muscle,  (g)  The  frontal  branch,  for  the  frontalis 
and  orbicularis  oculi  muscles,  (k)  The  parietal  branch  for  the  au- 
ricular muscles,  fascia  and  skin. 

8.  The  internal  maxillary  artery  (art.  maxittaris  interna)  is  the 
other  terminal  branch  of  the  external  carotid  artery.  This  is  under 
cover  of  the  parotid  gland  and  the  ramus  of  the  mandible.  The 
first  part  extends  from  the  neck  of  the  mandible  to  the  lower  margin 
of  external  pterygoid  muscle.  Its  main  branches  are  as  follows: 
(a)  Deep  auricular,  for  the  mandibular  articulation,  parotid  gland, 
external  auditory  meatus  and  the  tympanic  membrane,  (b)  The 
middle  meningeal  artery,  the  largest  branch,  enters  the  middle  fossa  of 
the  skull  through  the  foramen  spinosum.  It  gives  off  a  number  of 
branches  before  and  after  it  enters  the  skull.  These  are  mainly  for 
the  supply  of  the  meninges,  tympanic  cavity,  semilunar  ganglion  of 
the  trigeminal  nerve,  and  structures  in  the  orbit,  (c)  The  inferior 
alveolar  artery  enters  the  mandible  at  the  mandibular  foramen,  passes 
along  the  mandibular  canal  and  ends  at  the  mental  foramen  by 
dividing  into  mental  and  incisive  branches.  This  gives  rise  to 
branches  that  supply  the  mucous  membrane  of  the  cheek,  the 
mylohyoid  muscle,  all  of  the  teeth  and  the  quadratus  labii  inferior 
muscle. 

The  second  part  extends  from  the  lower  margin  of  the  external 
pyterygoid  muscle  to  upper  head  of  the  external  pterygoid  muscle. 
Its  branches  are  as  follows:  (a)  The  masseteric  artery,  for  that  mus- 
cle, (b)  The  two  deep  temporal  arteries,  for  the  temporal  muscle. 
(c)  The  pterygoid  branches,  for  these  muscles,  (d)  The  buccinator 
branch,  for  that  muscle,  the  mucosa  and  skin  of  the  cheek. 

The  third  part  extends  from  the  interval  between  the  two  heads  of 
the  external  pterygoid  muscle  through  the  pterygomaxillary  fissure 
into  the  pterygopalatine  fossa.  Its  branches  are  as  follows:  (a) 
The  infraorbital  branch  passes  through  the  orbit  in  the  infraorbital 
canal  and  appears  upon  the  face  at  the  infraorbital  foramen.  It 
supplies  branches  to  the  incisor  teeth,  the  maxillary  sinus,  some  of  the 
ocular  muscles,  the  lacrimal  gland,  the  lower  eyelid,  lacrimal  sac  and 


THE    SUBCLAVIAN    ARTERY  229 

skin  of  this  region,  (b)  The  posterior  superior  alveolar  artery  sup- 
plies the  molar  and  premolar  teeth,  the  gums  and  maxillary  sinus. 
(c)  The  descending  palatine  supplies  the  mucosa  of  the  roof  of  the 
mouth,  (d)  The  pharyngeal  branch  supplies  the  roof  of  the  nose 
and  pharynx,  the  sphenoidal  sinus  and  the  auditory  tube,  (e) 
The  sphenopalatine  branch  supplies  the  sphenoidal  sinus  and  the 
nasal  cavity. 

The  course  of  the  external  carotid  artery  is  indicated  by  a  line  drawn 
from  the  posterior  end  of  the  greater  cornu  of  the  hyoid  bone  to  the 
lobule  of  the  ear. 

The  internal  carotid  artery  (arteria  carotis  interna)  extends  from 
the  end  of  the  common  carotid  artery  to  the  middle  fossa  of  the  skull; 
it  enters  the  skull  through  the  carotid  canal  and  foramen  lacerum 
and  divides  into  the  middle  and  anterior  cerebral  arteries.  These 
are  considered  under  the  "Circulation  of  the  Brain,"  page  430,  with 
the  exception  of  the  ophthalmic  artery  (arteria  ophthalmica).  This 
artery  passes  into  the  orbit  through  the  optic  foramen  and  gives  off 
a  number  of  branches.  Some  of  these  are  for  the  muscle  of  the  eye- 
ball, others  for  the  lacrimal  gland  and  tissues  of  the  orbit,  nasal 
cavity,  eyelid,  ethmoidal  cells  and  meninges.  One  of  its  most  im- 
portant branches  is  the  central  retinal  artery  that  enters  the  eyeball 
through  the  optic  nerve  and  supplies  the  retina.  The  supraorbital 
branch  reaches  the  forehead  through  the  supraorbital  foramen  and 
supplies  the  frontalis  muscle  and  skin.  The  frontal  artery  is  the 
terminal  branch  of  the  ophthalmic  artery  and  supplies  the  scalp. 

The  subclavian  arteries  {arteria:  subclavian).  The  right  subclavian 
artery  is  shorter  than  the  left  as  it  arises  from  the  innominate  artery 
while  the  left  arises  from  the  arch  of  the  aorta.  The  right  one  is 
about  3  inches  (7.5  cm. )  in  length  while  the  left  is  about  4  inches  (10 
cm.)  in  length.  Each  consists  of  three  parts.  The  first  part  of  each 
extends  from  the  origin  to  the  medial  margin  of  the  scalenus  ante- 
rior muscle.  The  second  part  extends  from  the  medial  to  the  lateral 
margin  of  the  scalenus  anterior  muscle.  The  third  part  extends  from 
this  point  to  the  outer  margin  of  the  first  rib. 

The  branches  are  as  follows:  (a)  The  vertebral  artery  (art.  verte- 
bralis)  is  the  first  branch  and  it  passes  up  through  the  foramina  in  the 
upper  six  cervical  vertebra,  enters  the  skull  through  the  foramen 
magnum  and  anastomoses  with  the  vertebral  artery  of  the  other  side 
to  form  the  basilar  artery.  The  branches  are  given  under  the  "Cir- 
culation of  the  ''Brain,"  page  430. 

(b)  The  thyrocervical  trunk  (truncus  thyreoccrvicalis)  is  only  a  few 
millimeters  in  length  and  divides  into  three  branches:  (1)  The  inferior 
thyreoid  artery,  that  gives  branches  to  the  thyreoid  gland,  muscles  of 
the  neighborhood,  esophagus,  larynx,  trachea  and  the  structures 
within  the  vertebral  canal.     (2)  The  transverse  cervical  artery  (art. 


230 


THE   BLOOD-VASCULAR    SYSTEM 


transversus  colli)  that  terminates  as  the  ramus  ascendens,  or  super- 
ficial cervical  artery  and  the  ramus  descendens,  or  posterior  scapular 
artery.  These  vessels  supply  the  neighboring  muscles.  (3)  The 
transverse  scapular  artery  (art.  transversa  scapula)  terminates  in  the 
infraspinous  fossa  of  the  scapula.  It  gives  off  a  number  of  branches 
that  supply  the  dorsal  and  ventral  scapular,  sternomastoid  and  sub- 


Fig.   177.- — The  branches  of  the  subclavian  artery  and  the  course  of  the  vertebral  artery 
in  the  neck  (schematic).     (Sobotta  and  McMurrich.) 

clavius  muscles,  the  acromioclavicular,  sternoclavicular  and  shoulder 
joints. 

(c)  The  internal  mammary  artery  [art.  mammaris  interna)  extends 
from  its  origin  to  the  sixth  intercostal  space  where  it  divides  into  the 
musculophrenic  and  superior  epigastric  arteries.  This  lies  within  the 
thorax  and  gives  off  branches  to  the  diaphragm,  thymus,  medias- 
tinum, intercostal  spaces  and  the  skin.  The  musculophrenic  artery 
is  one  of  its  terminal  branches  and  this  supplies  the  diaphragm  and 


THE    AXILLARY    ARTERY  23 1 

the  lower  intercostal  spaces.  The  superior  epigastric  artery  continues 
into  the  abdominal  wall  and  anastomoses  with  the  inferior  epigastric 
artery.  It  gives  branches  mainly  to  the  muscles  and  skin  along  its 
course. 

(d)  The  costocervical  trunk  (truncus  costocervicalis)  gives  rise  to 
two  branches,  (i)  The  deep  cervical  artery  {art.  cervicis  profunda) 
passes  to  the  back  of  the  neck,  supplies  muscles  there  and  sends 
branches  into  the  vertebral  canal.  (2)  The  superior  intercostal 
artery  (art.  intercostalis  supremo)  gives  rise  to  the  first  two  dorsal 
intercostal  arteries  that  pass  ventrally  in  the  intercostal  spaces,  anas- 
tomose with  the  branches  from  the  internal  mammary  artery  and 
give  nutrient  branches  to  the  ribs. 

THE  AXILLARY  ARTERY  (ARTERIA  AXILLARIS)  AND  AXILLA 

The  axillary  artery,  the  continuation  of  the  subclavian  artery,  lies 
in  the  axillary  space  and  extends  from  the  outer  margin  of  the  first 
rib  to  the  lower  margin  of  the  tendon  of  the  teres  major  muscle.  It 
is  described  under  three  parts,  the  first  lying  above  the  upper  margin 
of  the  pectoralis  minor  muscle,  the  second  part  lying  under  cover  of 
that  muscle  and  the  third  part  constituting  the  remainder. 

The  branches  of  the  first  part  are  the  (a)  superior  thoracic  artery 
(art.  thoracis  suprema)  that  supplies  the  pectoralis  major  and  minor, 
subclavius,  serratus  anterior  and  intercostal  muscles,  (b)  The 
thoracoacromial  artery  (art.  thoracoacromialis)  a  short  trunk  that 
gives  off  four  branches;  the  clavicular  branch  supplies  the  sterno- 
clavicular articulation  and  adjacent  muscles;  the  pectoral  branch 
supplies  the  pectoral  and  deltoid  muscles  and  the  skin;  the  deltoid 
branch  supplies  the  deltoid  muscle  and  skin;  the  acromial  branch 
supplies  the  deltoid  muscle  and  completes  the  circulation  around 
the  shoulder. 

(c)  The  lateral,  or  long  thoracic  artery  (art.  thoracis  lateralis)  is 
a  branch  of  the  second  part.  It  passes  along  the  lower  margin  of 
the  pectoralis  minor  muscle  and  supplies  this  and  adjacent  muscles. 

The  remaining  branches  are  from  the  third  part  of  the  artery. 

(d)  The  subscapular  artery  (art.  subscapulars)  is  about  iJ-2  inches 
(3.7  cm.)  long  and  divides  into  two  branches,  the  circumflex  scapula:, 
or  dorsalis  scapulcB  artery  is  the  larger  and  gives  branches  to  the  in- 
fraspinatus, teres  major  and  minor,  triceps  and  deltoid  muscles. 
The  thoracodorsal,  or  long  subscapular  artery,  is  the  continuation  of 
the  main  stem  and  supplies  the  muscles  at  the  lateral  wall  of  the 
thorax. 

(e)  The  posterior  circumflex  artery  (art.  circumflexa  humeri 
posterior)  passes  to  the  back  of  the  neck  of  the  humerus  and  supplies 
the  teres  major  and  minor,  the  triceps  and  deltoid  muscles,  the 
shoulder  joint  and  the  head  of  the  humerus. 


232  THE    BLOOD-VASCULAR    SYSTEM 

(/)  The  anterior  circumflex  artery  (art.  circumflexa  humeri  anterior) 
is  small  and  passes  toward  the  bicipital  groove  supplying  the  long 
head  of  the  biceps  and  the  adjacent  muscles. 

The  course  of  the  axillary  artery  is  indicated  by  drawing  a  line  from 
the  middle  of  clavicle  to  the  lower  margin  of  the  pectoralis  major 
muscle  where  it  crosses  the  prominence  caused  by  thecoracobrachialis 
muscle.     The  arm  must  be  extended  at  a  right  angle. 

The  axillary  space,  or  axilla  is  a  pyramidal  space  situated  between 
the  upper  part  of  the  arm  and  the  side  of  the  thorax.  Its  apex  is 
directed  toward  the  root  of  the  neck  between  the  first  rib,  clavicle 
and  scapula  and  here  the  various  structures  enter  the  space.  The 
base,  formed  by  the  skin  and  axillary  fascia,  is  directed  downward 
and  outward.  The  ventral  wall  is  formed  by  the  pectoral  major 
and  minor  muscles,  the  clavicle,  the  costocoracoid  membrane  and 
the  subclavius  muscle.  The  dorsal  wall  is  formed  by  the  sub- 
scapularis,  teres  major  and  latissimus  dorsi  muscles.  The  medial 
boundary  consists  of  the  first  four  ribs  and  their  intercostal  muscles 
and  the  serratus  anterior  muscle.  The  lateral  boundary  is  narrow 
and  consists  of  the  humerus,  coracobrachialis  and  biceps  muscle. 
The  contents  are  the  axillary  artery  and  vein,  the  brachial  plexus  of 
nerves  and  its  branches,  some  branches  of  the  intercostal  nerves, 
lymph  nodes  and  fat. 

The  brachial  artery  {art.  brachialis)  is  the  continuation  of  the  axil- 
lary artery  and  extends  to  the  neck  of  the  radius.  It  courses  along 
the  medial  side  of  the  arm  and  gives  rise  to  several  branches,  (a) 
The  profunda  artery  (art.  profunda  brachii)  accompanies  the  radial, 
or  musculospiral  nerve.  It  supplies  the  triceps  and  shaft  of  the 
humerus  and  assists  in  forming  the  anastomosis  around  the  elbow 
joint. 

(b)  The  superior  ulnar  collateral,  or  inferior  profunda  artery  (art. 
collateralis  ulnaris  superior)  mainly  assists  in  the  anastomosis 
around  the  elbow  joint. 

(c)  The  inferior  ulnar  collateral,  or  anastomotic  artery  (art.  col- 
lateralis ulnaris  inferior)  supplies  the  triceps  and  brachialis  muscles 
and  aids  in  forming  the  anastomosis  around  the  elbow  joint. 

The  course  of  the  brachial  artery  is  indicated  by  drawing  a  line 
along  the  medial  margin  of  the  biceps  (at  the  junction  of  the  anterior 
and  middle  thirds  of  the  outlet  of  the  axilla)  to  the  middle  of  the 
elbow. 

At  the  neck  of  the  radius  the  brachial  artery  divides  into  radial 
and  ulnar  arteries. 

The  radial  artery  {art.  radialis)  is  the  smaller  and  extends  into 
the  palm  of  the  hand  forming  there  the  deep  palmar  arch.  Its  first 
part  extends  from  the  elbow  to  the  apex  of  the  styloid  process  of  the 
radius;  the  second  part  extends  around  the  side  of  the  wrist  to  the  first 


THE    ULNAR    ARTERY  233 

interosseous  space;  the  third  part  passes  into  the  palm  of  the  hand  to 
join  the  deep  branch  of  the  ulnar  artery. 

The  branches  of  the  first  part  are  the  radial  recurrent,  that  supplies 
the  brachioradialis,  supinator,  extensores  carpi  radialis  longus  and 
brevis  muscles  and  assists  in  the  anastomosis  around  the  elbow 
joint;  the  muscular  branches  for  the  muscles  of  the  radial  (ventral) 
side  of  the  forearm;  the  superficial  volar  artery  is  small  and  arises 
near  the  end  of  the  first  part,  passes  through  the  muscles  of  the  ball 
of  the  thumb  and  joins  the  main  part  of  the  ulnar  artery  to  form  the 
superficial  palmar  arch.  The  volar  carpal  branch  helps  form  the 
volar  carpal  arch  for  the  wrist  joint. 

The  branches  of  the  second  part  are,  the  dorsalis  pollicis  (two) 
that  pass  along  the  sides  (dorsally)  of  the  thumb  to  supply  the  skin, 
tendons,  ligaments  and  joints.  The  dorsalis  indicts  radialis  artery 
is  small  and  passes  along  the  radial  margin  of  the  index  finger  for 
the  skin,  tendon  and  joints.  The  first  dorsal  metacarpal  and  dorsal 
radial  carpal  arteries  are  small  and  pass  to  the  dorsal  aspect  of  the  palm. 

The  branches  of  the  third  part  are,  the  princeps  pollicis  which 
passes  to  the  distal  end  of  the  metacarpal  bone  of  the  thumb  and 
divides  into  two  branches  (collateral)  that  pass  along  the  sides  of  the 
thumb.  The  volaris  radialis  indicts  runs  along  the  radial  side  of 
the  index  finger. 

The  course  of  the  radial  artery  is  indicated  by  drawing  a  line  from 
the  hollow  of  the  center  of  the  elbow  to  the  side  of  the  styloid  process 
of  the  radius. 

The  ulnar  artery  extends  from  the  neck  of  the-  radius  to  the  palm 
of  the  hand  where  it  forms  the  superficial  palmar  arch  and  assists 
in  forming  the  deep  palmar  arch.  It  has  a  number  of  branches. 
(a)  The  volar  ulnar  recurrent  is  small  and  assists  in  forming  the  anas- 
tomosis around  the  elbow  joint,  (b)  The  dorsal  ulnar  recurrent 
supplies  the  brachialis  and  adjacent  muscles  and  assists  in  the  elbow 
joint  anastomosis,  (c)  The  common  interosseous  artery  extends  to 
the  superior  edge  of  the  interosseous  membrane  and  then  divides 
into  dorsal  and  ventral  interosseous  arteries.  The  ventral,  or  volar 
artery,  runs  between  the  deep  muscles  of  the  forearm  giving  branches 
to  these,  to  the  radius  and  the  ulna,  the  median  artery  and  other 
small  branches.  The  dorsal  artery  gives  off  the  interosseous  recurrent 
artery  (elbow- joint  anastomosis),  muscular  branches  to  the  deep 
muscles  of  the  back  of  the  forearm  and  branches  to  the  skin  of  this 
region  and  the  wrist,  (d)  The  volar  carpal  artery  is  small  and  assists 
in  the  carpal  arch  formation,  (e)  The  dorsal  carpal  artery  passes 
to  the  back  of  the  wrist  and  assists  in  forming  the  dorsal  carpal  arch. 
(/)  The  profunda  artery  is  the  last  branch  of  the  ulnar  artery  and 
passes  into  the  depths  of  the  palm  to  assist  in  forming  the  deep 
palmar  arch. 


234  THE   BLOOD-VASCULAR    SYSTEM 

The  course  of  the  ulnar  artery  is  indicated  by  two  lines,  as  the 
arterv  curves.  Draw  a  line  from  the  medial  epicondyle  of  the  hum- 
erus to  the  medial  surface  of  the  pisiform  bone;  the  distal  two-thirds 
represents  the  distal  two-thirds  of  the  ulnar  artery.  From  the  center 
of  the  cubital  fossa  draw  another  line  to  the  junction  of  the  upper 
and  middle  thirds  of  the  first  line  and  that  new  line  will  indicate 
the  course  of  the  first  part  of  the  ulnar  artery. 

In  front  of  the  elbow  joint  there  is  a  triangular,  somewhat  de- 
pressed area  called  the  cubital  fossa,  or  antecubital  space.  Here 
the  brachial  artery  sinks  in  quite  deeply.  The  base,  directed  up- 
ward, is  a  line  connecting  the  two  epicondyles  of  the  humerus.;  the 
medial  boundary  is  the  lateral  margin  of  the  pronator  teres;  the 
lateral  boundary  is  the  medial  margin  of  the  brachioradialis;  the  floor 
consists  of  the  supinator  and  brachioradialis.  This  space  contains 
the  brachial  artery  and  its  vena?  commites,  the  radial  and  ulnar 
arteries,  the  median  and  radial  nerves  and  the  tendon  of  the  biceps 
muscle. 

Upon  the  ventral  aspect  of  the  ligaments  of  the  wrist  lies  the 
ventral  or  volar  carpal  arch.  This  is  formed  by  the  volar  carpal 
branches  of  the  radial  and  ulnar  arteries  assisted  by  branches  from 
the  deep  palmar  arch  and  volar  interosseous  artery.  It  supplies 
the  ligaments  and  synovial  membranes  of  the  joints  here. 

The  dorsal  carpal  arch  is  similar  and  formed  by  the  dorsal  carpal 
branches  of  the  ulnar  and  radial  arteries  assisted  by  branches  from 
the  interosseous  arteries. 

The  superficial  palmar  arch  (areas  volaris  superficialis)  is  formed 
by  the  main  portion  of  the  ulnar  artery  and  the  superficialis  volae 
branch  of  the  radial  artery.  It  lies  just  beneath  the  deep  palmar 
aponeurosis.  It  gives  off  four  volar  cow  won  digital  arteries  of  which 
the  one  on  the  ulnar  side  passes  to  the  ulnar  side  of  the  little  finger. 
The  other  three  pass  to  the  clefts  between  the  fingers  where  each 
divides  into  two  branches  (proper  digital  arteries)  that  go  to  the 
adjacent  sides  of  index,  middle,  ring  and  little  fingers. 

The  position  of  the  superficial  palmar  arch  is  indicated  by  a  curved 
line  extending  from  the  pisiform  bone  to  the  base  of  the  cleft  between 
the  thumb  and  index  finger.  The  convexity  should  extend  to  about 
the  middle  third  of  the  palm. 

The  deep  palmar  arch  (arcus  volaris  profunda)  is  deeeply  placed. 
It  lies  upon  the  bases  of  the  metacarpal  bones  and  their  ligaments. 
It  gives  rise  to  recurrent  branches  for  the  volar  carpal  arch;  articular 
branches  of  the  adjacent  joints;  volar  carpal  arteries  that  pass  to  the 
dorsum  of  the  hand  and  form  the  digital  branches;  and  communicating 
branches  that  connect  with  the  proper  volar  digital  arteries. 

The  course  of  the  deep  palwar  arch  is  indicated  by  a  line  parallel  to  the 
line  of  the  superficial  arch  about  >£  to  %  inch  nearer   the  wrist. 


THE    DESCENDING   AORTA  235 

THE  DESCENDING  AORTA 

The  descending  aorta  (aorta  descendens)  begins  at  the  lower 
border  of  the  fourth  thoracic  vertebra,  passes  downward  (caudad) 
to  the  left  of  the  midline,  through  the  diaphragm  into  the  abdominal 
cavity  where  it  divides  ventral  to  the  body  of  the  fourth  lumbar 
vertebra  into  right  and  left  common  iliac  arteries.  That  portion 
(prediaphragmatic)  above  the  diaphragm  (above  the  twelfth  thoracic 
vertebra)  constitutes  the  thoracic  aorta  while  that  below  (post- 
diaphragmatic)  constitutes  the  abdominal  aorta. 

The  thoracic  aorta  (aorta  thoracalis)  is  7  to  8  inches  (17.5  to  20 
cm.)  in  length  and  is  reduced  in  diameter  from  23  mm.,  at  the 
beginning,  to  21  mm.,  at  the  diaphragm.     The  branches  are: 

(  Intercostal,  nine  pairs,  for  the  lower    nine  intercostal   spaces  that 

I      supply  the  intercostal  muscles,  the  vertebral  column  and  the  skin 

v    ■  ,  ,  of  the  back  and  sides  of  the  thorax, 

ranetai     J  0  ,  . 

I  subcostal,  one  pair. 

Superior  phrenic,  one   pair;   that  supply  the  superior  surface  of  the 

L      diaphragm. 

(Esophageal,  one  pair. 
Bronchial,  four  to  five  pairs. 
Pericardial,  three  to  four  pairs. 
Mediastinal,  several. 

The  abdominal  artery  (arteria  abdominalis)  extends  from  the 
twelfth  thoracic  vertebra  to  the  fourth  lumbar  vertebra,  is  from  7  to 
8  inches  (17.5  to  20  cm.)  in  length  and  lies  in  the  epigastric  and 
umbilical  regions.  Its  branches  may  be  divided  into  parietal  and 
visceral  but  they  will  be  given  in  order  of  origin. 

1.  Inferior  phrenic  (two)  parietal. 

\  Gastric. 

2.  Celiac  axis  (one)  visceral      \  Hepatic. 

[  Splenic. 

3.  Suprarenal  (two)  visceral. 

4.  First  lumbar  (two)  parietal. 

5.  Superior  mesenteric  (one)  visceral. 

6.  Renal  (two)  visceral. 

7.  Spermatic,  or  ovarian  (two)  visceral. 

8.  Second  lumbar  (two)  parietal. 

9.  Inferior  mesenteric  (one)  visceral. 

10.  Third  lumbar  (two)  parietal. 

11.  Fourth  lumbar  (two)  parietal. 

r>  -,.      ,.      -,       f  External  (two)  parietal. 

12.  Common  mac  (two)       {  T  %         .  ,     .  , 

(  Internal  (two)  parietal  and  visceral. 

13.  Middle  sacral  (one)  parietal. 

The  inferior  phrenic  arteries  supply  the  inferior,  or  abdominal 
surface  of  the  diaphragm  and  give  off  a  pair  of  superior  adrenal 
arteries. 


236 


THE   BLOOD-VASCULAR    SYSTEM 


The  celiac  axis  is  only  V2  inch  in  length  but  is  of  large  caliber. 
It  supplies  the  liver,  stomach,  spleen,  pancreas  and  part  of  the  duo- 
denum. Its  branches  are  as  follows:  the  left  gastric,  or  coronary; 
the  splenic,  which  gives  off  the  pancreatic,  short  gastric  (vasa  brevia) 
and  left  gastroepiploic  branches;  the  hepatic  artery  that  gives  off  the 
right  gastric,  gastroduodenal,  right  gastroepiploic  and  superior 
pancreaticoduodenale  arteries. 


The  suprarenal  arteries  supply  the  adrenal  glands  and  represent 
the  middle  suprarenal  arteries. 

The  superior  mesenteric  artery  supplies  the  duodenum,  jejunum, 
ileum,  cecum,  appendix,  ascending  and  transverse  colons.  Its 
branches  are  intestinal  (ten  to  sixteen)  for  the  jejunum  and  ileum; 
the  inferior  pancreaticoduodenale;  the  middle  colic;  right  colic,  ileo- 
colic and  terminal,  for  the  end  of  the  ileum,  cecum,  appendix, 
ascending  and  transverse  colons. 


THE   BRANCHES   OF    THE    ABDOMINAL    AORTA  237 

The  renal  arteries  are  two  large  arteries  that  supply  the  kidneys. 
Each  gives  off  the  inferior  suprarenals ,  ureteral,  perinephric  branches 
and  some  branches  to  the  lumbar  lymph  nodes. 

The  spermatic  (testicular)  arteries  accompany  the  vas  and  pass 
to  the  testes  in  the  spermatic  cords.  Each  gives  off  branches  to  the 
ureter,  peritoneum  and  lumbar  lymph  nodes. 

The  ovarian  arteries,  of  the  female,  pass  to  the  ovaries  and  uterus 
through  the  broad  ligament.  Each  gives  off  branches  to  the  ureter, 
peritoneum,  lumbar  lymph  nodes  to  the  uterine  tubes,  uterus  and 
its  round  ligament. 

The  inferior  mesenteric  artery  is  a  large  branch  that  supplies  the 
descending  colon,  iliac  and  pelvic  colons  and  the  upper  third  of  the 
rectum.  Its  branches  are  the  left  colic,  sigmoid  branches  and  the 
superior  hemorrhoidal  arteries. 

The  four  pairs  of  lumbar  arteries  correspond  to  the  intercostal 
arteries  of  the  thorax.  They  supply  the  muscles  and  skin  of  the 
dorsal  and  lateral  portions  of  the  abdominal  wall. 

The  middle  sacral  artery  is  a  small  artery  that  passes  along  the 
sacrum  and  coccyx  and  ends  in  the  coccygeal  gland. 

The  common  iliac  arteries  represent  the  terminal  branches  of  the 
aorta  and  start  at  the  middle  of  the  fourth  lumbar  vertebra  to  the 
left  of  the  midline.  The  right  artery  is  about  2  inches  (5  cm.)  in 
length  and  the  left  is  about  1%  inches  (4.3  cm.)  in  length.  Each 
divides  into  external  and  internal  iliac  arteries. 

The  internal  iliac,  or  hypogastric  artery  (arteria  hypogastrica), 
arises  opposite  the  sacroiliac  articulation  and  passes  into  the  pelvis 
for  about  1J-2  inches  (3.7  cm.)  before  dividing  into  its  terminal 
branches.  These  arteries  supply  the  greater  part  of  the  pelvic  wall 
and  viscera,  the  buttocks,  thighs  and  the  external  organs  of  repro- 
duction. Each  gives  rise  to  parietal  and  visceral  branches.  The 
parietal  branches  are  as  follows:  The  iliolumbar  artery  supplies 
the  iliacus,  psoas  and  quadratus  lumborum  muscles  and  also  the 
vertebral  canal.  The  lateral  sacral  artery  supplies  the  pyriformis 
muscle  and  also  sends  branches  to  the  sacral  canal  and  sacral  nerves. 
The  superior  gluteal  artery  leaves  the  pelvis  and  passes  into  the 
buttock  and  lies  on  the  deep  surface  of  the  gluteus  maximus.  It 
gives  off  a  number  of  muscular  branches  to  the  glutei,  obturator 
internus  and  tensor  fascia;  lata;  muscles  and  nutrient  vessels  to  the 
hip  bone.  The  obturator  artery  passes  into  the  buttock  and  gives 
off  a  number  of  muscular  branches  to  the  obturator  internus,  iliopsoas 
and  levator  ani  muscles;  nutrient  branches  to  the  ilium;  vesical 
branches  to  the  bladder;  pudic  branch  that  is  mainly  for  collateral 
circulation.  These  branches  all  arise  within  the  pelvis.  The 
terminal  part  of  the  artery  gives  off  branches  to  the  obturator 
externus  and  adjacent  muscles,  to  the  hip  joint,  head  of  the  femur 


238  THE    BLOOD-VASCULAR    SYSTEM 

and  ligaments.  The  internal  pudic  artery  is  a  large  branch  that 
enters  the  buttock  and  passes  to  the  perineum.  In  the  buttock  it 
supplies  the  neighboring  muscles.  In  the  perineum  it  gives  off  the 
inferior  hemorrhoidal  artery  that  supplies  the  lower  part  of  the  rectum 
and  the  anal  canal;  the  perineal  artery  for  the  scrotum  of  the  male, 
or  the  labia  of  the  female;  the  transverse  perineal  artery  supplies  the 
sphincter  ani,  the  sphincter  vagina;,  or  bulbocavernosus  muscle,  the 
bulb  of  the  urethra,  the  corpus  spongiosum  and  penile  portion  of 
the  urethra  (in  the  male)  and  the  bulb  of  the  vestibule  (in  the 
female) ;  the  profunda  artery  of  the  penis  or  elitoris  supplies  the  corpus 
cavernosum  of  the  penis  or  clitoris;  the  dorsal  artery  of  the  penis  or 
of  the  elitoris  supplies  the  dorsal  portion  of  the  penis  or  clitoris  as 
well  as  the  corpus  cavernosum  and  glans  penis,  or  clitoris.  The 
inferior  gluteal,  or  sciatic  artery  passes  into  the  buttock  and  then 
the  upper  part  of  the  thigh.  It  gives  of  muscular  branches  for  the 
proximal  parts  of  the  hamstring  muscles;  coccygeal  branch;  cutaneous 
branches  to  the  skin;  a  branch  that  accompanies  the  sciatic  nerve. 

The  visceral  branches  are  as  follows:  (a)  The  superior  vesical 
artery  supplies  the  upper  part  of  the  bladder.  (b)  The  inferior 
vesical  artery  supplies  the  base  of  the  bladder,  the  seminal  vesicles, 
vas  and  prostate  gland,  (c)  The  artery  of  the  ductus  deferens  accom- 
panies the  vas,  supplies  it  and  extends  to  the  testicle,  (d)  The 
middle  hemorrhoidal  artery  gives  branches  to  the  seminal  vesicles, 
vas,  prostate  and  terminates  in  the  rectum  where  it  supplies  the 
middle  third,  (e)  The  vaginal  artery  supplies  the  vagina  and  also 
the  rectum,  bulb  of  the  vestibule  and  base  of  the  bladder.  (J) 
The  uterine  artery  supplies  the  uterus,  round  ligament  and  the 
vagina. 

The  external  iliac  artery  (art.  iliaca  externa)  is  about  3^  to  4 
inches  (8.7  to  10  cm.)  in  length  and  ends  at  the  thigh  side  of  the 
inguinal  ligament.  It  gives  rise  to  two  main  branches.  The 
inferior  epigastric  artery  (art.  epigastrica  inferior)  passes  along  the 
medial  side  of  the  abdominal  inguinal  ring  into  the  ventral  ab- 
dominal wall  to  the  umbilical  region  where  it  anastomoses  with 
branches  from  the  superior  epigastric  branch  of  the  internal  mam- 
mary artery.  It  gives  rise  to  muscular  branches,  an  external  spermatic 
artery,  cutaneous  branches  and  a  pudic  branch.  The  deep  circum- 
flex iliac  artery  (art.  circumtlcxa  ilium  profunda)  passes  toward  the 
ventral  superior  spine  of  the  ilium  and  gives  off  muscular  and 
cutaneous  branches. 

The  femoral  artery  (arteria  femoralis)  is  the  continuation  of  the 
external  iliac  artery  and  extends  from  the  inguinal  ligament  to  the 
lower  part  of  the  thigh  where  it  passes  through  the  adductor  magnus 
muscle.  The  first  inch  and  a  half  was  called  the  common  femoral 
and  the  remainder  the  deep  and  superficial  portions.     Its  branches 


THE    POPLITEAL    ARTERY    AND    SPACE  239 

are  as  follows:  (a)  The  superficial  circumflex  iliac  artery  (art. 
circumflex  ilium  superficialis)  supplies  the  lymph  nodes  of  the 
groin  and  the  skin  here,  (b)  The  superficial  epigastric  artery  (art. 
epigastrica  superficialis)  passes  to  the  ventral  abdominal  wall  and 
supplies  the  superficial  fascia  and  skin  in  its  course,  (c)  The  super- 
ficial external  pudic  artery  (art.  pudenda  externa  superficialis)  sup- 
plies the  skin  of  the  pubis,  scrotal,  or  labial  regions,  (d)  The 
muscular  branches  pass  to  the  adductors,  pectineus,  sartorius  and 
vastus  medialis  muscles,  (e)  The  deep  external  pudic  artery  (art. 
pudendar  externa  profunda)  passes  to  the  scrotum  or  labium  majus. 
(f)  The  deep  femoral  artery  (art.  profunda  femoralis)  is  the  largest 
branch  of  the  femoral  artery  and  passes  in  between  the  deep  muscles 
of  the  thigh  and  gives  rise  to  numerous  branches.  These  are  the 
lateral  circumflex,  medial  circumflex,  muscular  and  four  perforating 
arteries.  These  are  for  the  supply  of  the  deep  muscles  of  the  thigh 
and  the  perforating  arteries  pass  to  the  dorsal  part  of  the  thigh  and 
anastomose  with  vessels  there,  (g)  The  anastomotic  artery,  or  arteria 
genu  suprema,  supplies  the  skin  of  the  medial  side  of  the  leg  muscles 
near  the  knee  and  the  knee  joint. 

The  course  of  the  femoral  artery  is  indicated  by  a  line  drawn  from 
a  point  midway  between  the  ventral  superior  spine  of  the  ilium 
and  the  symphysis  pubis  to  the  adductor  tubercle  on  the  medial 
condyle  of  the  femur.  The  superior  two-thirds  of  this  line  represents 
the  femoral  artery.  The  thigh  should  be  abducted  and  rotated 
laterally. 

The  popliteal  artery  (art.  poplitea)  is  the  continuation  of  the 
femoral  artery  back  of  the  knee;  it  lies  in  the  popliteal  fossa  at  the 
distal  end  of  which  it  divides  into  anterior  and  posterior  tibial  arteries. 
It  is  deeply  placed  and  gives  rise  to  the  following  branches:  Muscular 
branches  to  the  hamstring  and  upper  leg  muscles;  articular  (five) 
branches  to  the  knee  joint;  cutaneous  branches  to  the  skin  of  the 
popliteal  space. 

The  popliteal  fossa,  or  space,  is  back  of  the  knee  joint  and  is  of  a 
diamond  shape.  It  is  bounded  superolaterally  by  the  biceps; 
inferolaterally  by  the  lateral  head  of  the  gastrocnemius  and  plantaris; 
supermedially  by  the  semimembranosus,  semitendinosus,  sartorius 
and  gracilis;  infcromedially  by  the  medial  head  of  the  gastrocnemius. 
The  floor  is  formed  by  the  popliteal  plane  of  the  femur,  the  dorsal 
ligament  of  the  knee  joint  and  the  fascia  covering  the  popliteus 
muscle.  It  contains  the  popliteal  artery  and  its  branches,  the 
popliteal  vein,  the  termination  of  the  external  saphenous  vein,  the 
common  peroneal  (external  popliteal)  and  tibial  (internal  popliteal) 
nerves,  some  lymph  nodes  and  fat. 

The  course  of  the  popliteal  artery  i^  indicated  by  a  line  drawn  from 
the  outer  margin  of  the  semimembranosus  muscle  (at  the  beginning 


240  THE    BLOOD-VASCULAR    SYSTEM 

of  the  lower  third  of  the  thigh)  to  the  middle  of  the  popliteal  space; 
this  indicates  the  upper  part  of  the  artery.  The  lower  part  Is  repre- 
sented by  a  line  drawn  from  this  point  vertically  downward  to  the 
level  of  the  tuberosity  of  the  tibia. 

The  anterior  tibial  artery  (art.  tibialis  anterior)  is  the  smaller 
branch  of  the  popliteal  artery  and  passes  distally  upon  the  ventral 
surface  of  the  interosseous  membrane.  It  gives  off  the  following 
branches:  (a)  Fibular  branch  that  supplies  the  soleus,  peroneus 
longus  and  skin  of  this  region,  (b)  The  posterior  tibial  recurrent 
branch  for  anastomosis  around  the  knee  joint,  (e)  The  anterior 
tibial  recurrent  is  for  the  same  purpose  and  also  supplies  the  tibialis 
anterior  and  the  tibiofibular  articulation,  (d)  Muscular  branches 
for  the  muscles  of  the  front  of  the  leg.  (e)  Cutaneous  branches  for 
the  skin  of  the  front  of  the  leg.  (/)  Medial  anterior  malleolar  branch 
for  the  skin  of  the  lateral  malleolus  and  the  ankle  joint,  (g)  The 
lateral  anterior  malleolar  branch  for  the  skin  of  that  region  and  the 
ankle  joint  and  adjoining  articulations. 

The  dorsalis  pedis  artery  is  the  direct  continuation  of  the  anterior 
tibial  artery.  It  extends  from  the  front  of  the  ankle  joint  to  the 
base  of  the  first  interosseous  space.  Its  branches  are  as  follows: 
(a)  Cutaneous  branches  for  the  skin  of  the  dorsum  and  medial  side 
of  the  foot,  (b)  Medial  and  lateral  tarsal  branches  that  supply  the 
extensor  digitorum  brevis  and  the  articulations  here,  (c)  The 
arcuate  artery  arches  across  the  bases  of  the  metatarsal  bones  and 
gives  off  first  three  metatarsal  arteries;  each  of  these  divides  into 
digital  arteries  that  supply  the  adjacent  sides  of  the  outer  four  toes. 
(</)  The  first  dorsal  metatarsal  artery  arises  from  the  dorsalis  pedis 
artery  and  supplies  the  two  sides  of  the  great  toe  and  the  medial 
side  of  the  next  toe.  (e)  The  profunda  artery  passes  through  the 
foot  to  the  plantar  part  and  anastomoses  with  vessels  there. 

The  course  of  the  anterior  tibial  artery  is  indicated  by  drawing  a 
line  from  the  inner  side  of  the  head  of  the  fibula  to  a  point  midway 
between  the  two  malleoli.  All  of  this  line,  except  the  first  i>4 
inches,  represents  the  artery. 

The  course  of  the  dorsalis  pedis  artery  is  indicated  by  drawing  a 
line  from  the  point  midway  between  the  two  malleoli  to  the  base 
of  the  first  interosseous  space. 

The  posterior  tibial  artery  is  the  larger  branch  of  the  popliteal 
artery.  It  lies  between  the  superficial  and  deep  muscles  of  the  back 
of  the  leg  and  extends  from  the  lower  margin  of  the  popliteus  muscle 
to  a  point  midway  between  the  medial  malleolus  and  the  most 
prominent  part  of  the  heel,  where  it  divides  into  medial  and  lateral 
plantar  arteries. 

It  gives  off  the  following  branches:  (a)  Muscular  brandies  to  the 
soleus,  tibialis  posterior,  flexor  digitorum  longus  and  flexor  hallucis 


THE    PLANTAR    ARTERIES  24.I 

longus.  (b)  A  fibular  branch  to  the  adjacent  muscles  and  for 
anastomosis  around  the  knee  joint,  (c)  The  peroneal  artery  is  its 
largest  branch  and  passes  to  the  dorsal  part  of  the  lateral  malleolus. 
It  gives  off  muscular  branches  to  the  muscles  along  its  course;  a 
nutrient  branch  to  the  fibula;  a  communicating  branch  to  the  posterior 
tibial  artery;  a  perforating  artery  that  passes  along  the  inferior  margin 
of  the  interosseous  membrane  to  the  front  of  the  ankle  and  anas- 
tomoses with  the  vessels  here.  (</)  The  nutrient  artery  supplies  the 
tibia,  (e)  The  communicating  branch  that  communicates  with  the 
peroneal  artery.  (/)  Cutaneous  branches  for  the  skin  of  the  medial 
and  dorsal  surfaces  of  the  leg.  (g)  The  posterior  medial  malleolar 
branch  anastomoses  with  the  corresponding  branch  of  the  anterior 
tibial  artery. 

The  course  of  the  posterior  tibial  artery  is  indicated  by  drawing  a 
line  from  a  point  i  inch  below  the  center  of  the  popliteal  space  to  a 
point  midway  between  the  medial  malleolus  and  the  most  prominent 
part  of  the  heel. 

The  plantar  arteries  are  medial  and  lateral. 

The  medial  plantar  artery  ( art.  plantar  is  medialis)  is  the  smaller, 
passes  along  the  medial  side  of  the  foot  to  the  head  of  the  metatarsal 
bone  of  the  great  toe;  here  it  is  joined  by  a  branch  of  the  dorsalis 
pedis  artery  and  supplies  the  medial  side  of  the  great  toe  and  the 
muscles,  skin  and  articulations  along  its  course.  It  also  gives  off 
three  branches  that  join  the  metatarsal  branches  of  the  lateral 
plantar  artery. 

The  lateral  plantar  artery  (art.  plantaris  lateralis)  is  deeply  placed, 
courses  toward  the  lateral  side  of  the  foot  and  at  the  base  of  the  fifth 
metatarsal  bone  it  arches  medially  to  the  base  of  the  first  metatarsal 
bone  where  it  anastomoses  with  the  dorsalis  pedis  artery.  The 
arched  part  constitutes  the  plantar  arch. 

The  branches  of  the  main  vessel  are  as  follows:  (a)  Muscular 
branches  to  the  muscles  of  the  foot,  (b)  Cutaneous  branches  to 
the,  lateral  side  of  the  foot,  (c)  The  media!  calcaneal  branch  to  the 
skin  and  tissues  of  the  heel.  The  arch  gives  off  the  following 
branches:  (d)  Four  plantar  metatarsal  arteries  that  form  the  digital 
arteries  that  supply  the  adjacent  sides  of  the  four  inner  toes,  (e) 
Three  perforating  arteries  that  join  the  dorsal  metatarsal  arteries. 
(/  Articular  branches  to  the  tarsal  joints,  (g)  The  fifth  metatarsal 
branch  supplies  the  outer  side  of  the  little  toe,  the  joints  and  tendon 
sheathes  along  its  course. 

The  course  of  the  medial  plantar  artery  is  indicated  by  a  line  drawn 
from  the  point  midway  between  the  medial  malleolus  and  the  promi- 
nence of  the  heel  to  a  point  at  the  middle  of  the  under  surface  of  the 
great  toe.  The  course  of  the  lateral  plantar  artery  is  indicated  by  a 
line  from  the  same  starting  point  to  a  point  about  }2  inch  internal 


242 


THE    BLOOD-VASCULAR    SYSTEM 


to  the  tuberosity  of  the  little  toe.  The  plantar  arch  is  indicated  by 
a  line  drawn  from  this  point  transversely  across  the  foot  to  the  base 
of  the  first  interosseous  space. 

VEINS  (VEN.fi) 

The  blood  passes  from  the  arteries  to  the  capillaries  and  then  is 
carried  by  the  veins  to  the  heart.     The  main  veins  are  the  superior 

Superficial  Temporal  Vein  Middle  Temporal  re/'n 


Occip,tal 


Posterior  Huricu/ar  V 
Posterior  Tac'al  V. 


Posterior  Externa  I  Jufu/arV '. 
External  Jugular  K 


Fig.  179. — The 


i  o£  the  right  side  of  the  head  and  neck. 


and  inferior  venae  cavae,  the  pulmonary  veins  and  the  azygos  system. 
The  blood  is  returned  from  the  head  and  neck  chiefly  by  the 
internal  jugular  veins  (right  and  left)  which  correspond  to  the  com- 
mon carotid  arteries.  The  blood  that  enters  the  cranial  cavity  by 
means  of  the  internal  carotid  and  vertebral  arteries  is  carried  to  the 
venous  sinuses  of  the  skull  (see  the  "Circulation  of  the  Brain"). 
Of  these  sinuses  the  transverse  sinus  on  each  side  continues  as  the 


THE    VEINS    OF    THE    SUPERIOR    EXTREMITY  243 

internal  jugular  vein.  This  vein  passes  down  the  neck,  in  the  carotid 
sheath,  and  behind  the  sternoclavicular  articulation  each  is  joined 
by  the  corresponding  subclavian  vein  forming  the  innominate  vein 
of  each  side.  The  tributaries  to  each  internal  jugular  vein  are  the 
common  facial,  lingual,  pharyngeal,  superior  and  middle  thyreoid 
veins. 

The  common  facial  vein  receives  the  blood  from  parts  supplied 
by  several  of  the  branches  of  the  external  carotid  artery.  The 
anterior  facial  division  corresponds  to  the  external  maxillary  artery 
while  the  posterior  facial  vein  corresponds  to  the  temporal  and  in- 
ternal maxillary  branches  of  the  external  carotid  artery. 

The  lingual  vein  corresponds  to  the  lingual  artery. 

The  pharyngeal  veins  start  at  the  venous  plexus  of  the  pharynx 
and  represent  the  various  branches  distributed  to  the  pharynx. 

The  occipital  vein  corresponds  to  the  occipital  artery. 

The  superior  and  middle  thyreoid  veins  correspond  to  the  branches 
of  the  superior  thyreoid  artery. 

The  external  jugular  vein  is  in  the  neck  but  it  is  a  tributary  of  the 
subclavian  vein.  This  vein  is  formed,  back  of  the  angle  of  the 
mandible,  by  a  branch  of  the  posterior  facial  and  the  posterior  au- 
ricular veins.  This  receives  the  transverse  cervical,  transverse  scapu- 
lar and  anterior  jugular  veins  and  is  usually  quite  large. 

The  blood  of  the  superior  extremity  is  returned  ultimately  by  the 
subclavian  vein. 

In  the  hand  the  blood  is  returned  from  the  fingers  by  the  superficial 
volar  and  dorsal  digital  veins  (a  pair  of  each  to  each  finger).  These 
vessels  anastomose  with  each  other  on  the  dorsal  and  ventral  por- 
tions of  the  palm  and  through  the  palm  and  carry  the  blood  to  the 
vessels  of  the  forearm. 

In  the  forearm  there  are  two  main  (superficial)  longitudinal  venous 
channels,  the  cephalic  vein  on  the  radial  side  and  the  basilic  vein 
on  the  ulnar  side  and  occasionally  a  median  vein  on  the  ventral 
surface.  The  cephalic  vein  starts  from  the  radial  side  of  the  dorsal 
venous  arch  of  the  palm  and  turns  to  the  radial  side  of  the  ventral 
surface;  it  continues  to  the  cubital  fossa  and  from  there  continues 
up  the  arm  on  the  lateral  margin  of  the  biceps  muscle  to  the  interval 
between  the  deltoid  and  pectoralis  major  muscles,  near  the  clavicle; 
here  it  turns  in  and  empties  into  the  axillary  vein  of  which  it  is  a 
tributary.  In  the  cubital  fossa  it  is  connected  to  the  basilic  vein  by 
the  median  cubital  vein  which  also  connects  it  with  the  deep  veins 
of  the  forearm. 

The  basilic  vein  begins  on  the  ulnar  side  of  the  dorsal  venous 
plexus  of  the  hand  and  continues  along  the  dorsal  surface  of  the 
forearm  to  the  upper  third  of  the  forearm  where  it  turns  to  the 
ventral  surface;  it  continues  into  the  arm  along  the  medial  margin 


244 


THE    BLOOD-VASCULAR    SYSTEM 


s 


^\ 


of  the  biceps  muscle,  and  at  about  the  middle  it  pierces  the  fascia 
and  accompanies  the  branchial  artery  and  in  the  axilla  continues  as 
the  axillary  vein.     The  median  cubital  vein  connects  it  to  the  cephalic 

and  deep  veins  of  the  forearm. 
The  median  vein,  when  pres- 
ent, starts  at  the  plexus  in  the 
palm,  continues  along  the  ven- 
tral surface  of  the  forearm  and 
at  the  cubital  region  receives 
the  deep  median  vein  and  then 
divides  into  median  cephalic 
and  median  basilic  veins  that 
empty  into  the  corresponding 
veins.  The  median  cubital 
vein  is  then  absent. 

Deep    veins    accompany    the 
various  arteries  (as  vena  com- 
mites)  and  carry  the  blood  to 
the  axillary  vein. 
"""         The  axillary  vein  {vena  axil- 
laris) starts  at  the  lower  mar- 
i,-c  v.     gin  of  the    teres  major  muscle 
and  is  the  direct  continuation 
v""      of    the   basilic   vein.     At     the 
lower  margin  of  the  first  rib  it 
continues    as    the    subclavian 
vein.      Its    tributaries   are   the 
cephalic  vein  and  the  vena  com- 
mites  of  the  brachial  artery. 

The  subclavian  vein  {vena 
subclavia)  extends  from  the 
lower  margin  of  the  first  rib  to 
the  dorsal  surface  of  the  sternal 
end  of  the  clavicle  where  it  is 
joined  by  the  internal  jugular 
vein  to  form  the  innominate. 
Its  main  tributary  is  the  ex- 
ternal jugular  vein. 

The    innominate    veins    are 
spect   right  and  left. 

The  right  innominate  vein 
{vena  innomyna  dexter)  is  about 
i  inch  (2.5  cm.)  in  length  and  extends  from  the  medial  extremity 
of  the  right  clavicle  to  a  little  inferior  to  the  cartilage  of  the  first 
(right)  rib.  Its  course  is  almost  vertical  and  close  to  the  right 
margin  of  the  sternum. 


Median  CephaJ/c 
Ve,n  r 

Lateral  Cutanea 


CephaJia  Vein  - 


-Superficial  veins  of  the  flexor 
of  the  upper  extremity. 


THE    SUPERIOR   VENA    CAVA 


245 


The  left  innominate  vein  (vena  itmomyna  sinister)  is  about  2j^ 
inches  (6  cm.)  in  length  and  extends  from  the  medial  extremity  of 
the  left  clavicle  obliquely  downward  and  to  the  right  to  join  the 
right  innominate  vein  to  form  the  superior  vena  cava.  This  junc- 
tion is  just  inferior  to  the  first  right  costal  cartilage.  The  tributaries 
to  the  innominate  veins  are  the  vertebral,  inferior  thyreoid  and  internal 
mammary  veins. 

The  superior  vena  cava,  or  precava  (vena  cava  superior),  is  about  3 
inches  (7.5  cm.)  in  length  and  extends  from  the  inferior  margin  of 


"RC<m.  Co-  flrt 


"R  Safari 


Ih}.Tl««"'<1^ 


Lisflrt 


181. — Arch  of  the  aorta  and  its  branches;  the  superior  vei 
the  pulmonary  arteries  and  veins. 


id  its  tributaries; 


the  first  right  costal  cartilage  to  the  level  of  the  upper  margin  of  the 
third  right  costal  cartilage,  where  it  empties  into  the  right  atrium 
of  the  heart.  Its  course  is  vertical  and  its  inferior  half  is  within 
the  pericardium.  In  addition  to  the  innominate  veins  it  also 
receives  the  vena  azygos  major.- 

The  superficial  veins  of  the  inferior  extremity  are  the  great  and 
small  saphenous  veins. 

The  great  saphenous  vein  (vena  saphena  magna)  begins  at  the 
dorsal  venous  arch  which  is  formed  by  the  dorsal  digital  veins  of 
the  foot.  From  the  medial  side  of  this  arch  the  great  saphenous 
vein  passes  in  front  of  the  medial  malleolus,  along  the  medial  margin 
of  the  tibia  to  the  back  of  the  medial  condyle  of  the  femur;  it  then 
gradually  turns  to  the  ventral  surface  of  the  thigh  and  at  the  fossa 


246 


THE    BLOOD-VASCULAR    SYSTEM 


ovalis  (saphenous  opening)  it  passes  through  the  deep  fascia  and 
empties  into  the  femoral  vein.  It  receives  tributaries  from  the 
dorsum  of  the  foot,  the  front  and  back  of  the  leg,  from  the  front  and 


femora/  rfrfery 

Superficial  fyi'fastrictfetr, 

FemoraJ  Vein 


FlG.    182. — The  superficial  veins  of  the  lower  extremity 
its  tributaries.     B,  the  small  saphenous  * 

back  of  the  thigh  (the  superficial  femoral  veins)  and  the  superficial 
circumflex  iliac,  superficial  epigastric  and  superficial  external  pudic 
veins. 

The  small  saphenous  vein  (vena  saphena  parva)  starts  at  the  lateral 


THE    INFERIOR   VENA   CAVA  247 

portion  of  the  venous  arch  of  the  foot,  passes  back  of  the  lateral 
malleolus,  up  the  dorsal  surface  of  the  calf  to  about  its  middle  where 
it  pierces  the  fascia  and  passes  to  the  popliteal  space  to  empty 
into  the  popliteal  vein  It  receives  tributaries  from  the  back  and 
lateral  surfaces  of  the  heel  and  leg. 

The  deep  veins  of  the  foot  and  leg  are  two  in  number  for  each 
artery  and  are  called  vena  commitcs.  In  the  popliteal  space  the 
venae  commites  of  the  anterior  and  posterior  tibial  veins  join  to 
form  the  popliteal  vein.  This  vein  receives  the  small  saphenous 
vein  and  tributaries  that  correspond  to  the  branches  of  the  popli- 
teal artery. 

The  femoral  vein  accompanies  the  femoral  artery  and  is  the 
continuation  of  the  popliteal- vein.  Its  tributaries  are  the  great 
saphenous  vein  and  vessels  that  correspond  to  branches  of  the 
femoral  artery. 

The  external  iliac  vein  is  the  direct  continuation  of  the  femoral 
vein  and  at  the  level  of  the  lumbosacral  articulation  it  is  joined  by 
the  internal  iliac  or  hypogastric  vein  to  form  the  common  iliac  vein 
of  each  side.  Its  tributaries  are  the  deep  circumflex  Viae  and  inferior 
epigastric  veins. 

The  internal  iliac  or  hypogastric  vein  (vena  hypogastrica)  is  short 
and  is  formed  by  the  junction  of  vessels  that  correspond  to  the 
branches  of  the  hypogastric  artery.  Its  tributaries  are  superior  and 
inferior  gluteal,  inferior  hemorrhoidal,  lateral  sacral,  middle  hemor- 
rhoidal, uterine  (two  veins  from  the  uterine  plexus),  vaginal  (one 
vein  from  the  vaginal  plexus),  veins  from  the  superior  and  inferior 
vesical  plexuses  and  the  vesicoprostatic  plexus,  and  the  dorsal  veins 
of  the  penis,  or  clitoris. 

The  common  iliac  veins  are  right  and  left. 

The  right  common  iliac  vein  (vena  iliaca  communis  dexter)  is 
smaller  and  more  vertical  in  direction  than  the  left.  The  tributaries 
to  each  common  iliac  vein  are  the  middle  sacral  (to  the  left)  and  the 
iliolumbar s  to  both. 

The  inferior  vena  cava,  or  postcava  (vena  cava  inferior)  is  formed 
by  the  junction  of  the  two  common  iliac  veins  on  the  right  side  of 
the  body  of  the  fifth  lumbar  vertebra.  It  passes  through  the  ab- 
domen, through  the  diaphragm,  enters  the  pericardium  and  empties 
into  dorsoinferior  portion  of  the  right  atrium  of  the  heart.  Its 
tributaries  are  the  inferior  phrenic,  suprarenal,  renal,  spermatic,  or 
ovarian,  lumbar  and  hepatic  veins.     (See  Fig.  178.) 

The  inferior  phrenic  veins  (two)  return  a  part  of  the  blood  from 
the  diaphragm. 

The  suprarenal  veins  (two)  return  the  blood  from  those  glands. 

The  renal  veins  (two)  return  the  blood  from  the  kidneys.  The 
right  renal  vein  is  about  1  inch  (2.5  cm.)  in  length  and  the  left  is  about 
3  inches  (7.5  cm.)  in  length. 


248 


THE    BLOOD-VASCULAR    SYSTEM 


The  lumbar  veins  are  four  pairs  of  veins  that  correspond  to  the 
four  pairs  of  lumbar  arteries. 

The  spermatic,  or  testicular  veins  (two)  return  the  blood  from  the 
testes.  Each  vein  begins  at  the  pampiniform  plexus  of  veins  upon 
the  spermatic  cord,  passes  through  the  inguinal  canal,  enters  the 
abdomen  and  that  of  the  right  side  empties  into  the  inferior  cava 
while  that  of  the  left  side  empties  into  the  left  renal  vein. 

The  ovarian  vein  of  each  side  starts  at  the  pampiniform  plexus  of 
veins  and  terminates  like  the  corresponding  vein  of  the  male. 


-RCo»  -Car. /Ire  Ui-p*"** 


_  L  "Phrenic  M 

a  Subclo* 

\    fin. 


Lisflrt 


Fig.    183. — Arch    of    the    aorta    and  its  branches;  the  superior  vena  cava  and  its  tribu- 
taries; the  pulmonary  arteries  and  veins. 

The  blood  that  passes  from  the  aorta  through  the  celiac  axis, 
superior  and  inferior  mesenteric  arteries  does  not  pass  directly  to  the 
inferior  cava  but  passes  first  through  the  liver  (through  the  portal 
vein).  The  blood,  after  passing  through  the  liver,  leaves  this  organ 
through  two  vessels  called  the  hepatic  veins;  these  open  into  the 
inferior  vena  cava  just  before  this  vessel  passes  through  the 
diaphragm.     This  peculiar  course  constitutes  the  portal  circulation. 

The  pulmonary  veins  are  usually  five  in  number,  three  right  and 
two  left.  These  start  at  the  root  of  the  lung  and  the  two  left  proceed 
directly  to  the  left  atrium  where  they  empty  their  blood.  On  the 
right  side  the  veins  from  the  superior  and  middle  lobes  of  the  lung 
usually  unite  to  form  one  vessel  and  this  and  the  vein  from  the  inferior 
lobe  proceed  directly  to  the  left  atrium  where  they  empty  their 
blood. 


THE    AZYGOS   VEINS 


249 


The  azygos  veins,  three  in  number,  collect  the  blood  from  most 
of  the  intercostal  spaces  and  serve  to  connect  the  superior  and 
inferior  venae  cava?. 

The  azygos  major  (vena  azygos  major)  arises  opposite  the  first 
or  second  lumbar  vertebra  by  a  branch  from  the  right  lumbars, 
right  renals  or  inferior  vena  cava.  It  passes  up  the  right  side  of 
the  vertebral  column,  through  the  aortic  orifice  in  the  diaphragm 


Fig.   184. — The  portal  vein  and  its  tributaries. 

to  the  fourth  thoracic  vertebra  where  it  arches  over  the  root  of  the 
right  lung  to  empty  into  the  superior  vena  cava.  Its  tributaries 
are  the  lower  ten  posterior  intercostal  veins  of  the  right  side,  the 
right  superior  intercostal  vein,  the  azygos  minor  veins,  the  right 
bronchial  vein  and  several  veins  from  the  esophagus,  mediastinum 
and  pericardium. 

The  vena  azygos  minor  inferior  (vena  hemiazygos)  arises  in  the 
abdomen  by  a  branch  from  one  of  the  left  lumbar  veins  or  from  the 


25° 


THE    BLOOD-VASCULAR    SYSTEM 


left  renal  vein.  It  enters  the  thorax  through  the  left  crus  of  the 
diaphragm  and  passes  upward  to  the  ninth  or  eighth  thoracic 
vertebra  where  it  passes  across  to  the  right  and  terminates  in  the 
vena  azygos  major.  Its  tributaries  are  the  lower  one  or  two  inter- 
costals  and  veins  from  the  esophagus  and  mediastinum. 


MaJor:     n    J' 


Fig.   185. — The  azygos  system  of  veins. 

The  vena  azygos  minor  superior  (vena  azygos  accessoria)  is  usually 
small  and  joins  the  vena  azygos  major  or  the  preceding  vessel. 

THE  SYSTEMIC  CIRCULATION 

The  general  systemic  circulation  is  as  follows:     The  blood  leaves 
the  left  ventricle  through  the  aorta  and  through  the  branches  at 


THE    PORTAL    CIRCULATION  25 1 

the  arch  is  distributed  to  the  head,  neck  and  upper  extremities. 
From  the  thoracic  aorta  it  is  distributed  to  the  lesser  organs  and 
walls  of  the  thorax  and  partly  to  the  lungs,  from  the  abdominal  aorta 
to  the  walls  and  viscera  of  the  abdomen  and  pelvis,  and  lastly  to  the 
lower  extremities.  The  blood  from  the  head  and  upper  extremities 
is  returned  upon  each  side  through  the  internal  jugular  and  sub- 
clavian veins  respectively.  On  each  side  these  form  the  innomi- 
nate or  brachiocephalic  veins  which  join  to  form  the  superior  vena 
cava  that  empties  the  blood  into  the  right  atrium.  From  the  lower 
extremities  the  blood  is  returned  by  the  two  common  femoral  veins, 
which  continue  as  the  external  iliac  veins  in  the  abdomen  and  are 
joined  by  the  internal  iliac  veins  to  form  the  common  iliac  vein  of 
each  side.  The  common  iliac  veins  unite  to  form  the  inferior  vena 
cava  which  then  receives  the  blood  through  the  tributaries  above 
mentioned.     The  blood  is  then  emptied  into  the  right  atrium. 

The  portal  circulation  is  as  follows:  The  blood  leaves  the  aorta 
through  the  celiac  axis,  superior  and  inferior  mesenteric  arteries. 
From  the  celiac  axis  the  blood  passes  to  the  liver,  stomach,  spleen, 
pancreas  and  duodenum.  From  the  inferior  mesenteric  artery  it 
passes  to  the  pancreas,  duodenum,  jejunum,  ileum,  cecum,  appendix, 
ascending  and  transverse  colons.  From  the  inferior  mesenteric 
artery  the  blood  passes  to  the  descending  colon,  sigmoid  flexure  and 
upper  part  of  the  rectum.  The  blood  from  the  spleen,  most  of 
that  from  the  stomach,  pancreas  and  duodenum  is  returned  by  the 
splenic  vein;  that  from  the  distribution  of  the  superior  mesenteric 
artery  by  the  superior  mesenteric  vein;  that  from  the  distribution 
of  the  inferior  mesenteric  artery  by  the  inferior  mesenteric  vein. 
The  inferior  mesenteric  vein  joins  the  splenic  vein  and  the  splenic 
vein  then  joins  the  superior  mesenteric  vein  to  form  the  portal 
vein. 

The  portal  vein  (vena  porta)  is  about  3  inches  (7.5  cm.)  long,  passes 
upward  and  to  the  left,  enters  the  transverse  fissure  of  the  liver  where 
it  divides  into  two  main  branches,  the  right  and  left  lobar  branches. 


CHAPTER  V 
THE  LYMPH  VASCULAR  SYSTEM 

The  lymp  vascular  system  is  in  close  relation  to  the  blood  vascular 
system  and  through  it  the  liquor  sanguinis  of  the  blood,  as  lymph, 
comes  into  direct  contact  with  the  cells  of  the  body.  It  differs  from 
the  blood  vascular  system  in  several  ways:  (i)  It  contains  no  blood 
but  lymph.  (2)  The  flow  is  in  one  direction,  from  the  periphery 
toward  the  center.  (3)  It  is  no  true  circulatory  system  as  it  has  no 
separate  organ  to  force  the  lymph  along.  (4)  Like  the  veins,  many 
of  the  lymph  vessels  possess  valves  but  unlike  veins  these  lymph 
vessels  are  interrupted  at  frequent  intervals  by  lymph  nodes  through 
which  the  lymph  must  filter  before  it  can  course  onward.  These 
lymph  vessels  communicate  directly  with  the  large  serous  cavities 
of  the  body  (peritoneal,  pleural,  pericardial,  joint  cavities,  bursa? 
and  tendon  sheaths)  by  means  of  stornata.  These  serous  cavities 
are  really  enormously  dilated  lymph  spaces  lined  with  endothelial 
cells. 

This  system  consists  of  lymph  spares,  lymph  vessels,  lymphatic 
organs  and  the  lymph. 

Lymph  spaces  do  not  represent  the  beginning  of  the  lymph  vessel 
system  but  here  the  lymph  has  its  origin  and  passes  from  these 
spaces  into  the  vessels.  They  are  mere  tissue  spaces  and  are  not 
lined  with  endothelial  cells  except  in  a  few  isolated  instances,  as 
those  around  the  ganglion  cells  of  the  sensor  ganglia,  and  the  large 
lymph  space  above  mentioned.  There  are  three  sets  of  these  spaces: 
(1)  the  intercellular,  or  pericellular;  (2)  the  perineural,  around  the 
nerves;  (3)  the  perivascular,  around  the  blood-vessels. 

The  lymph  vessels  (vasa  lympkatica)  vary  in  size,  the  smallest 
being  capillarics'tha.t  are  mere  tubes  of  endothelial  cells  and  varicose 
in  form.  It  is  into  these  that  the  lymph  passes  directly  from  the 
intercellular  spaces.  The  next  vessels  are  thin-walled  and  resemble 
venules,  and  lastly,  the  largest  are  the  lymphatic  and  thoracic  ducts. 
Certain  structures  as  the  brain,  cartilage,  epidermis,  nails  and  avas- 
cular structures  are  devoid  of  lymphatic  vessels. 

The  lymphatic  organs  are  the  cistcrna  chvli,  lymph  nodes,  spleen, 
thymus  and  tonsils,  and  lymphoid  tissue  comprising  the  diffuse  form, 
solitary  nodules  and  Pcyer's  patches. 

Lymph  nodes  are  collections  of  lymphoid  tissue  varying  in  size 
from  that  of  a  pin  head  to  that  of  a  lima  bean.  They  are  scattered 
152 


CISTERNA    CHYLI 


L.J««V 


ThorCcrf 


throughout  the  body,  being  usually  arranged  in  groups.  The 
lymph  must  filter  through  one  or  more  groups  before  it  enters  the 
blood  vascular  system. 

The  lymph  is  practically  the  liquor  sanguinis  of  the  blood  con- 
taining only  the  leukocytes,  or  white  blood  cells.  It  passes  out  of 
the  blood  capillaries  into  the  tis- 
sue spaces,  bathes  the  tissues 
and  cells,  giving  up  its  nutritive 
elements  and  receiving  effete  ma- 
terial in  return.  It  then  passes 
through  the  walls  of  the  lymph 
capillaries  entering  here  the  real 
vessel  system.  It  then  passes 
into  the  larger  vessels,  through 
one  or  more  node  groups  and  is 
ultimately  returned  to  the  blood 
vascular  system  by  the  right 
lymphatic  and  thoracic  ducts. 
These  empty  into  the  right  and 
left  subclavian-internal  jugular 
vein  junctions,  respectively. 

Throughout  the  body  the  lym- 
phatics are  divided  into  a  super- 
ficial and  a  deep  set.  The  super- 
ficial set  drains  the  outside  of  the 
organs  and  the  body,  while  the 
deep  set  drains  the  muscles,  bones 
and  deeper  parts  of  the  organs. 
This  will  be  further  explained  as 
the  various  structures  are  dis- 
cussed. 

The  receptaculum  chyli  (cis- 
tema  chyli)  is  a  delicate,  thin- 
walled  reservoir,  5  to  7.5  cm. 
long  and  6  to  8  mm.  wide.  It  is 
located  in  the  abdominal  cavity 
on  the  right  side  of  the  first  or 
second  lumbar  vertebra  between 
the  aorta  and  the  vena  azygos 
major.  This  thin-walled  struc- 
ture is  difficult  to  find  when  empty.  It  receives  the  lymph  from 
various  regions  through  the  following  tributaries:  two  ascend- 
ing lumbar  trunks,  two  descending  (lumbar)  trunks,  one  com- 
mon intestinal  trunk  and  occasionally  one  retroaortic  trunk.  It  is 
drained  by  the  thoracic  duct. 


CsChyH 


-Cisterna  chyli  and    thoracic 
1L.  first  lumbar  vertebra. 


254  THE    LYMPH   VASCULAR    SYSTEM 

The  thoracic  duct  is  15  to  18  inches  (37.5  to  45  cm.)  long  and 
starts  from  the  cisterna  chyli  at  about  the  first  lumbar  vertebra. 
It  passes  up  (cephalad)  through  the  aortic  orifice  of  the  diaphragm 
into  the  thoracic  cavity  (dorsal  mediastinum)  in  the  midline  to  the 
level  of  the  fifth  or  fourth  thoracic  vertebra  where  it  crosses  to  the 
left  side  of  the  vertebral  column.  It  continues  through  the  superior 
mediastinum  into  the  neck  to  the  level  of  the  seventh  cervical  verte- 
bra where  it  curves  downward  over  the  subclavian  artery  and 
empties  into  the  angle  formed  by  the  left  subclavian-internal  jugular 
vein  junction.  Its  orifice  is  guarded  by  a  valve  and  valves  are 
numerous  along  its  course.  The  thoracic  duct  receives  the  lymph 
from  the  lower  extremities,  the  abdomen  and  its  contents,  the  left 
thorax,  left  lung  and  the  left  side  of  the  heart,  from  part  of  the  lower 
half  of  the  right  thorax  and  from  the  left  side  of  the  head  and  neck 
and  the  left  upper  extremity. 

The  right  lymphatic  duct  (ductus  lymphaticus  dexter)  is  about 
%  inch  in  length.  It  is  formed  by  the  junction  of  the  right  sub- 
clavian, the  right  jugular  and  right  bronchomediastinal  trunks  and 
empties  into  the  right  subclavian-internal  jugular  vein  junction. 
Its  orifice  is  guarded  by  a  valve.  The  right  lymphatic  duct  receives 
the  lymph  from  the  right  side  of  the  head  and  neck,  the  right  upper 
extremity,  the  right  thorax  (upper  half),  the  right  lung,  the  right 
side  of  the  heart  and  from  part  of  the  convex  surface  of  the  liver. 

For  the  sake  of  convenience  the  lymphatic  drainage  of  the  body 
will  be  considered  in  regions,  as  head  and  neck,  upper  extremity, 
lower  extremity,  abdomen  and  thorax. 

LYMPHATICS  OF  THE  HEAD  AND  NECK 

The  lymphatics  of  the  outside  of  the  head  and  neck  are  divided 
into  superficial  and  deep.  The  node  groups  of  the  head  are  as  follows 
(those  marked  (S)  are  superficial  and  those  marked  (D)  are  deep): 

1.  Occipital  (Lym  phoglandulo?  occipitalcs)  (S). — This  group  con- 
sists of  one  to  three  nodes  in  the  occipital  region  on  the  upper  part 
of  the  trapezius  muscle;  these  drain  the  occipital  portion  of  the 
scalp  and  their  efferents  carry  the  lymph  to  the  upper  deep  cervical 
nodes. 

2.  Postauricular  (Lym phoglandula:  auricularcs  posteriores)  (S). — 
This  group  comprises  usually  two  or  three  nodes  near  the  mastoid 
process  of  the  temporal  bone.  These  drain  the  posterior  temporo- 
parietal region,  part  of  the  pinna  of  the  ear  and  the  posterior  wall  of 
the  external  auditory  canal.  Their  efferents  carry  the  lymph  to 
the  upper  deep  cervical  nodes. 

3.  Preauricular  (L.  auricularcs  antcriores)  (S  and  D). — The 
superficial  nodes  are  placed  over  the  parotid  gland  and  the  deep  are 
within  its  substance.     The  latter  are  the  more  numerous.     These 


LYMPHATICS    OF    THE    HEAD 


255 


nodes  drain  the  eyelids,  eyebrows,  frontotemporal  part  of  the  scalp, 
root  of  the  nose,  the  front  wall  of  the  external  auditory  canal,  part 
of  the  pinna,  the  middle  ear,  soft  palate,  deep  portion  of  the  cheek 
and  back  part  of  the  nasal  fossae.  Their  efferents  drain  into  the 
upper  deep  cervical  nodes. 

4.  The  superficial  facial  (L.  facialis  superficialis)  (S). — This  group 
consists  of  three  subgroups:  (a)  the  infraorbital,  or  maxillary  nodes 


Su\j  mental 
Cerv 


Jug  Trim  K 


Fig.  187. — Lymph  nodes  and  lymphatic  drainage  of  the  head  and  neck.     Superficial  nodes 
indicated  as  circles  and  deep  nodes  in  solid  black. 

in  the  infraorbital  region;  (b)  the  buccal  or  buccinator  group  in  the 
cheek;  (c)  the  supramandibular  group  upon  the  mandible  at  the 
anterior  edge  of  the  masseter  muscle.  These  groups  drain  the  eye- 
lid, conjunctiva,  skin  and  mucous  membrane  of  the  nose  and  cheek. 
Their  efferents  carry  the  lymph  to  the  submaxillary  nodes  and  to 
the  upper  deep  cervical  nodes. 

5.  Deep  facial  (L.  faciales  profunda)  (D). — This  group  consists  of 
several  nodes  along  the  lateral  wall  of  the  pharynx  near  the  internal 


256  THE    LYMPH  VASCULAR    SYSTEM 

maxillary  artery.  These  drain  orbit,  temporal  fossa,  the  naso- 
pharynx, palate,  nasal  fossa;  and  the  cerebral  meninges.  Their 
efferents  pass  to  the  upper  deep  cervical  nodes. 

6.  Lingual  (L.  linguales)  (D)  nodes  are  at  the  base  of  the  tongue 
and  are  intervening  nodes  in  the  tongue  drainage.  Their  lymph 
passes  into  the  upper  deep  cervical  nodes. 

The  node  groups  of  the  neck  are  as  follows: 

Superficial  cervical  (L.  cervicales  superficiales)  (S). — These  com- 
prise the  external  jugular  group  that  lies  upon  the  external  jugular 
vein  just  a  little  below  the  parotid  gland.  These  nodes  drain  the 
lower  part  of  the  pinna  of  the  ear,  the  parotid  region,  the  occipital 
and  mastoid  regions  and  their  efferents  pass  to  the  upper  deep  cervical 
and  supraclavicular  nodes. 

2.  Submaxillary  (L.  submaxillares)  (D). — This  consists  of  three 
to  six  nodes  located  in  the  submaxillary  triangle.  These  drain  the 
superficial  part  of  the  nose,  lower  and  front  part  of  the  face,  upper 
and  lower  lips,  gums,  anterior  part  of  the  margin  of  the  tongue  and 
the  floor  of  the  mouth,  either  directly  or  through  the  facial  and 
submental  nodes.  Their  efferents  carry  the  lymph  to  the  upper 
deep  cervical  nodes. 

3.  The  submental,  or  suprahyoid  nodes  (S)  lie  beneath  the  fascia 
just  within  the  symphysis  of  the  mandible;  they  drain  the  skin  of 
the  chin,  skin  and  mucous  membrane  of  the  middle  of  the  lower 
lip,  the  gums,  the  floor  of  the  mouth  and  the  tip  of  the  tongue. 
Their  efferents  pass  to  the  submaxillary  and  upper  deep  cervical 
nodes. 

4.  The  prelaryngeal  nodes  (D)  are  variable  and  when  present  are 
found  in  front  of  the  lower  (tracheal)  end  of  the  larynx.  They  drain 
the  lower  part  of  the  larynx,  the  upper  part  of  the  trachea  and  the 
thyreoid  body.  Their  efferents  carry  the  lymph  to  the  upper  deep 
cervical  nodes. 

5.  The  pretracheal  nodes  (D)  lie  upon  the  front  of  the  trachea 
and  receive  the  lymph  from  the  trachea  and  thyreoid  body.  Their 
efferents  pass  to  the  upper  deep  cervical  nodes. 

6.  The  retropharyngeal  nodes  (L.  retropharyngeal)  (D)  lie  behind 
the  upper  part  of  the  dorsal  wall  of  the  pharynx  and  drain  the  nasal 
fossae,  the  nasopharynx  and  the  auditory  tubes.  Their  efferents 
pass  to  the  upper  deep  cervical  nodes. 

7.  The  deep  cervical  nodes,  although  the}-  form  an  almost  con- 
tinuous chain,  are  divided  into  two  sets,  the  upper  and  the  lower. 
Each  group  may  be  divided  into  medial  and  lateral  subgroups. 
The  upper  lie  beneath  the  sternomastoid  muscle  (the  lateral  sub- 
group) and  upon  the  internal  jugular  vein  (the  medial  subgroup). 
These  drain  the  occipital  region  of  the  scalp,  the  back  of  the  neck, 
the  pinna  of  the  ear,  the  tongue,  larynx,  trachea,  thyreoid  body, 


THE    LYMPHATICS    OF    UPPER    EXTREMITY  257 

nasopharynx,  palate,  nasal  fossae,  esophagus  and  face  through  the 
above-mentioned  node  groups.  The  lower  group  lies  in  relation  with 
the  lower  part  of  the  internal  jugular  vein  (medial  subgroup)  and  in 
relation  with  the  brachial  plexus  and  the  subclavian  artery  (lateral 
subgroup).  This  group  drains  the  back  of  the  neck,  scalp,  the  super- 
ficial pectoral  region  in  addition  to  receiving  lymph  from  the  upper 
deep  nodes.  The  lymph  from  the  upper  nodes  passes  partly  to  the 
lower  nodes  and  partly  into  a  trunk  that  joins  a  similar  trunk  from 
the  lower  nodes.  These  two  trunks  unite  to  form  the  jugular  lymph 
trunk  upon  each  side  of  the  neck.  Upon  the  right  side  of  the  body 
this  trunk  joins  the  subclavian  trunk  to  form  the  right  lymphatic 
duct,  while  upon  the  left  side  it  empties  into  the  thoracic  duct,  or 
directly  into  the  subclavian-jugular  vein  junction. 

THE  UPPER  EXTREMITY 

The  nodes  and  vessels  of  the  upper  extremity  are  superficial  and 
deep.     They  are  as  follows: 

The  superficial  cubital  nodes  (L.  cubitales  superficiales)  (S)  are 
the  first  nodes  of  the  extremity.  These  are  located  upon  the  medial 
side  of  the  basilic  vein  just  above  the  medial  epicondyle.  They 
drain  both  surfaces  of  the  hand  and  forearm  and  also  its  ulnar  border. 
Their  efferents  pass  to  the  deep  cubital  or  the  lateral  axillary  nodes. 

2.  The  Deep  Cubital  Nodes  (L.  cubitales  profunda)  (D). — Occa- 
sionally some  small  nodes  are  found  along  the  ulnar  and  radial 
arteries.  The  deep  cubital  nodes,  however,  lie  at  the  terminal  part 
of  the  brachial  artery  upon  the  volar  side  of  the  elbow;  they  drain 
the  deep  structures  of  the  hand  and  forearm.  The  efferents  pass 
to  the  lateral  axillary  nodes. 

3.  The  axillary  group  \L.  axillares)  (D)  comprises  the  following 
subgroups: 

(a)  The  lateral  axillary  nodes  (one  to  six)  lie  along  the  axillary 
vein.  They  receive  the  lymph,  both  superficial  and  deep,  from 
the  ventral  and  dorsal  pectoral  regions  either  directly  or  through 
the  node  groups  previously  mentioned.  Their  efferents  pass  to  the 
central  axillary  nodes  and  the  subclavian  group  and  even  to  the 
lower  deep  cervical  nodes. 

(b)  The  ventral  axillary,  or  pectoral  nodes  (two  to  four)  lie 
along  the  lower  border  of  the  pectoralis  major  muscle  from  the  third 
to  the  sixth  intercostal  spaces;  they  receive  the  lymph  from  the 
superficial  part  of  the  ventral  and  lateral  thoracic  walls  above  the 
umbilicus  and  the  lateral  two-thirds  of  the  mammary  gland.  Their 
efferents  pass  to  the  central,  lateral  and  subclavian  nodes. 

(c)  The  dorsal  axillary,  or  subscapular  nodes  lie  upon  the  dorsal 
wall  of  the  axilla  near  the  subscapular  artery.     They  drain   the 


258 


THE    LYMPH    VASCULAR    SYSTEM 


superficial  parts  of  the  dorsal  and  lateral  walls  of  the  thorax  above 
the  level  of  the  umbilicus  and  the  lower  part  of  the  neck.  Their 
efferents  carry  the  lymph  to  the  central  group,  or  to  the  subclavian 
nodes,  or  even  to  the  jugular  trunk. 

(d)   The  central  axillary  group  consists  of  three  to  six  large  nodes 
near  the  base  of  the  axilla.     They  drain  more  or  less  completely  the 


bctav 
VartlC 


-Lymph  nodes  and  lymphatic  drainage  of  the  upper  i 
and  thoracic  wall.     RLD,  Right  lymphati 


preceding  groups.     Their  efferents  carry  the  lymph  to  the  subclavian 
group. 

4.  The  deltopectoral  nodes  (S)  lie  in  the  interval  between  the 
pectoralis  major  and  the  deltoid  muscles.  They  receive  the  lymph 
from  the  outer  side  of  the  shoulder  and  arm.  Their  efferents  pass 
to  the  lateral  axillary  nodes,  or  the  lower  deep  cervical  group. 

5.  The  subclavian  nodes  (infraclavicular)  (D)  lie  upon  the  axillary 
artery  between  the  pectoralis  minor  muscle  and  the  clavicle.     They 


THE    LYMPHATICS    OF    LOWER    EXTREMITY 


259 


HP&tecrj'c 


receive  the  lymph  from  the  upper  extremity,  ventral,  lateral,  and 
dorsal  thoracic  walls  and  mammary  gland.     From  these  nodes  the 
subclavian  trunk   carries    the  lymph  ir— 
though    some    efferents    may    pass 
to  the  lower  deep  cervical  nodes. 

Upon  the  right  side  the  jugular  and 
subclavian  trunks  unite  to  form  the 
shortright  lymphatic  duct  that  empties 
into  the  junction  of  the  right  sub- 
clavian and  internal  jugular  veins. 
Upon  the  left  side  they  may  empty 
into  the  thoracic  duct,  or  into  the 
left  subclavian-internal  jugular  vein 
junction. 

THE  LOWER  EXTREMITY 

The  lymphatics  of  the  lower  ex- 
tremity are  superficial  and  deep. 
The  node  groups  are  as  follows: 

1.  The  anterior  tibial  nodes  (D)  is 
inconstant  and  when  the  present  is 
located  at  the  upper  part  of  the 
anterior  surface  of  the  interosseous 
membrane.  It  receives  the  lymph 
from  the  deep  parts  of  the  sole,  the 
dorsum  of  the  foot  and  deep  struc- 
tures of  the  front  of  the  leg.  The 
efferents  pass  to  the  popliteal  nodes. 

2.  The  popliteal  nodes  (L.  poplitea) 
(D)  are  four  or  five  in  number  and 
lie  in  the  popliteal  space  around  the 
popliteal  artery.  They  receive  lymph 
from  the  deep  parts  of  the  foot,  deep 
structures  of  back  of  the  calf  and  from 
the  anterior  tibial  node,  also  from  the 
superficial  structures  of  the  lateral 
part  of  the  foot  and  heel  and  back  1 
of  the  leg  (parts  drained  by  the  ex- 
ternal  saphenous  vein).  The  efferents 
carry  the  lymph  to  the  deep  femoral 
nodes.  Occasionally  a  node  is  found  where  the  small  saphenous 
vein  pierces  the  deep  fascia. 

3.  The  inguinal  nodes  are  divided  into  two  sets,  the  superficial 
and  deep.     The  superficial  inguinal  nodes  (L.  ingninales  superficiales) 


9. — Lymph  nodes  and  lymphatic 
nage  of  the  lower  extremity. 


260  THE  LYMPH  VASCULAR  SYSTEM 

consist  of  two  sets,  proximal  and  distal  and  they  lie  superficial 
to  the  deep  fascia.  The  superior,  or  proximal  superficial  inguinal 
nodes,  four  to  seven  in  number,  lie  just  below  the  inguinal  ligament 
and  above  a  horizontal  line  drawn  through  the  middle  of  the 
saphenous  opening  in  the  deep  fascia.  They  receive  the  lymph 
from  the  outer  and  back  part  of  the  thigh  and  buttock,  the  super- 
ficial part  of  the  abdominal  wall  (below  the  umbilicus),  the  anal 
canal,  the  perineum,  scrotum  and  penis  of  the  male  and  the  labia, 
vestibule  and  vagina  of  the  female.  The  lymph  then  passes  into 
the  deep  inguinal  nodes. 

The  inferior,  or  distal  superficial  inguinal  nodes  lie  below  the 
above  nodes  around  the  internal  saphenous  vein  and  number  three 
to  six.  They  receive  the  lymph  from  the  superficial  parts  of  the 
foot  (not  lateral),  the  sole  (except  the  heel),  inner,  front  and  sides 
of  the  calf,  and  all  the  superficial  parts  of  the  thigh  except  the  upper 
and  outer  parts.     The  efferents  pass  to  the  deep  inguinal  nodes. 

The  deep  inguinal  nodes  (L.  subinguinales  profunda?),  three  to 
seven,  lie  along  the  femoral  vein.  They  receive  the  lymph  from  the 
popliteal  and  superficial  inguinal  nodes  as  well  as  from  the  deep 
structures  of  the  outer  and  front  portions  of  the  thigh,  also  deep 
parts  of  the  clitoris  and  penis.  The  efferents  carry  the  lymph 
to  the  external  iliac  nodes  of  the  abdomen. 

THE  LYMPH  NODES  OF  THE  ABDOMEN 

The  lymph  nodes  of  the  abdomen  are  divided  into  two  groups,  the 
parietal  and  visceral.  The  parietal  drain  the  deep  structures  of 
the  walls  and  extremities,  while  the  visceral  drain  the  viscera. 
The  groups  are  as  follows: 

Parietal  Visceral 

i.  External  iliac  [  i.  Celiac 

2.  Internal  iliac  Preaortic      j  2.  Superior  mesenteric 

3.  Common  iliac  1 3.  Inferior  mesenteric 

4.  Subaortic. 

5.  Lateral  aortic 

6.  Retroaortic 

1.  The  external  iliac  nodes  consist  of  three  chains,  one  lateral, 
one  intermediate  and  one  medial  to  the  external  iliac  artery.  These 
nodes  receive  the  lymph  from  the  lower  extremity  through  the 
various  inguinal  nodes,  from  the  glans  penis  or  the  glans  clitoris, 
the  deeper  structures  of  the  abdominal  wall  (below  the  umbilicus), 
from  the  upper  part  of  the  vagina,  cervix  of  the  uterus,  prostate, 
bladder,  membranous  urethra,  some  from  the  internal  iliac  nodes 
and  from  the  structures  along  the  course  of  the  obturator  artery. 
The  efferents  carry  the  lymph  to  the  common  iliac  nodes. 


THE    LYMPHATICS    OF    THE    ABDOMEN 


26l 


2.  The  internal  iliac,  or  hypogastric  nodes  (L.  hypogastrica),  sur- 
round the  internal  iliac  artery.  They  receive  the  lymph  from  the 
pelvic  viscera  and  the  deeper  structures  of  the  perineum,  buttocks, 
posterior  part  of  the  thigh  and  urethra.  The  efferents  carry  the 
lymph  to  the  common  iliac  nodes. 

A  special  group,  the  sacral  nodes  (L.  sacrales)  lies  in  the  hollow  of 
the  sacrum  and  drain  the  rectum,  prostate  and  dorsal  pelvic  wall. 
The  efferent  pass  to  the  subaortic  and  lateral  aortic  nodes. 

3.  The  common  iliac  nodes  are  arranged  in  groups  in  front,  lateral 
and  medial  to  the  common  iliac  artery.  They  receive  the  lymph 
from  the  external  and  internal  iliac  nodes  and  send  it  to  the  lateral 
aortic  nodes. 


4.  The  subaortic  nodes  (L.  subaortic^)  lie  upon  the  ventral  sur- 
face of  the  fifth  lumbar  vertebra  and  receive  part  of  the  lymph  from 
the  sacral  and  hypogastric  nodes  and  pass  the  lymph  to  the  lateral 
aortic  nodes. 

5.  The  lateral  aortic  or  lumbar  nodes  (L.  lambales)  comprise  two 
seis  right  and  left,  at  the  respective  sides  of  the  aorta.  On  each  side 
the  nodes  receive  the  lymph  from  the  corresponding  common  iliac, 
subaortic  and  hypogastric  nodes;  from  the  testicle,  or  ovary,  oviduct 
and  body  of  the  uterus;  from  the  lateral  abdominal  muscles;  from 
the  kidneys  and  adrenals.  The  chief  vessels  from  these  nodes  are 
the  right  and  left  ascending  {common)  lumbar  trunks  that  empty  the 
lymph  into  the  cisterna  chyli. 


262  THE    LYMPH   VASCULAR    SYSTEM 

6.  The  retroaortic  nodes  lie  behind  the  aorta  on  the  third  and 
fourth  lumbar  vertebrae.  They  receive  lymph  from  the  lateral  and 
preaortic  nodes  and  the  chief  vessel  from  this  group  is  the  retroaortic 
trunk  that  empties  into  the  cisterna  chyli. 

The  visceral  nodes  of  the  abdomen  proper  are  the  preaortic  nodes 
consisting  of  three  main  groups  and  a  large  number  of  subsidiary 
groups. 

1.  The  celiac,  or  middle  suprapancreatic  group  consists  of  nodes 
around  the  origin  of  the  celiac  axis  artery.  In  addition  there  are 
several  subsidiary  groups. 

(a)  The  gastric  group  (L.  gastricce)  comprise  the  left  ventral 
gastric  nodes  that  lie  between  the  layers  of  the  lesser  omentum  along 
the  left  gastric  artery;  they  drain  most  of  the  lesser  curvature  and 
the  neighboring  parts  of  the  ventral  and  dorsal  surfaces  of  the  stomach 
and  empty  into  the  left  dorsal  gastric  nodes. 

(b)  The  dorsal  paracardial  nodes  {right  and  left)  lie  around  the 
cardiac  orifice  and  drain  the  cardiac  end  of  the  stomach  and  the 
efferents  pass  to  the  left  dorsal  gastric  nodes. 

(c)  The  left  dorsal  gastric  nodes  lie  upon  the  left  gastric  artery 
and  receive  lymph  from  the  cardiac  part  of  the  stomach  and  from 
the  above  nodes.  The  efferents  pass  to  the  middle  suprapancreatic 
(celiac)  nodes. 

(d)  The  right  gastroepiploic  nodes  lie  along  the  right  part  of  the 
greater  curvature  of  the  stomach,  receive  lymph  from  that  part  and 
pass  the  lymph  to  the  subpyloric  nodes. 

(e)  The  subpyloric  nodes  are  located  at  the  end  of  the  first  part 
of  the  duodenum  and  drain  the  pyloric  part  of  the  stomach  and 
receive  lymph  from  the  right  gastroepiploic  nodes.  Their  efferents 
pass  to  the  celiac  group. 

(/)  The  left  suprapancreatic,  or  the  pancreaticosplenic  nodes  are 
distributed  along  the  course  of  the  splenic  artery  and  drain  the  spleen 
and  the  left  portion  of  the  stomach  and  empty  into  the  middle 
suprapancreatic  or  celiac  group. 

(g)  The  right  suprapancreatic  nodes  lie  upon  the  hepatic  artery 
and  drain  a  part  of  the  liver  and  the  pyloric  portion  of  the  stomach. 
The  lymph  then  passes  to  the  middle  suprapancreatic  or  celiac 
group. 

(//)  The  biliary  nodes  lie  along  the  bile  duct  and  receive  lymph 
from  the  gall-bladder  and  liver  and  pass  it  to  the  celiac  nodes. 

(0  The  hepatic  nodes  lie  at  the  portal  fissure  of  the  liver,  receive 
lymph  from  the  liver  and  pass  it  to  the  celiac  nodes. 

From  the  celiac,  or  middle  suprapancreatic  nodes  the  lymph  is 
carried  by  the  celiac  trunk  to  the  common  intestinal  trunk  and  also 
common  lumbar  trunks. 

2.  The  superior  mesenteric  group  is  found  around  the  origin  of 


THE    LYMPHATICS    OF    THE    INTESTINES  263 

the    superior    mesenteric    artery.     Its    subsidiary  groups  are:  (a) 
mesenteric,  (b)  ileocolic  and  (c)  mesocolic  nodes. 

(a)  The  mesenteric  nodes,  comprising  from  100  to  150,  lie  between 
the  layers  of  the  mesentery.  One  group  lies  close  to  the  intestinal 
wall,  another  around  the  loops  and  primary  branches  of  the  artery 
and  a  third  along  the  main  stem  of  the  artery.  The  lymph  from  the 
small  intestine  drains  through  the  first  group,  then  into  and  through 
the  second  and  then  through  the  third  group  and  is  then  carried 
to  the  superior  mesenteric  nodes. 


RPul-aC»<-iKl1 


GaStric 
■R  CaStric 

Supra|>o.n. 


& 


=*t      m     vV\°v 

Fig.    191. — Lymph  nodes  and  lymphatic  drainage  of  the  stomach. 

(b)  The  ileocolic  nodes,  about  twenty  to  thirty,  form  a  chain  along 
the  ileocolic  artery.  The  main  subgroups  are  the  ileal,  along  the 
ileal  branch  of  the  superior  mesenteric  artery;  the  ventral  ileocolic 
near  the  front  of  the  cecum;  the  dorsal  ileocolic,  in  the  angle  between 
the  ileum  and  the  colon;  the  appendicular  along  the  appendix  and 
paracolic  along  the  medial  side  of  the  ascending  and  transverse  colons. 
These  nodes  drain  the  lower  part  of  the  ileum,  cecum,  appendix  and 
ascending  colon  and  empty  the  lymph  into  the  superior  mesenteric 
nodes. 

(c )  The  mesocolic  nodes  (part  of  the  paracolic  chain)  are  numerous 
and  lie  in  relation  with  the  transverse  colon.     The  lymph  from  the 


264 


THE    LYMPH    VASCULAR    SYSTEM 


transverse  colon  passes  through  these  nodes  and  thence  to  the 
superior  mesenteric  nodes.  From  the  superior  mesenteric  group 
the  Ivmph  is  drained  by  the  superior  mesenteric  trunk  that  helps  to 
form  the  common  intestinal  trunk. 

3.  The  inferior  mesenteric  group  lies  at  the  origin  of  the  inferior 
mesenteric  artery.  The  subsidiary  groups  are  the  (a)  left  colic, 
(b)  sigmoid,  (c)  pararectal. 

(a)  The  left  colic  -nodes  lie  along  the  branches  of  the  left  colic 
artery  and  drain  the  descending  colon  and  empty  into  the  inferior 
mesenteric  group. 

(b)  The  sigmoid  nodes  lie  along  the  branches  of  the  sigmoid  and 
superior  hemorrhoidal  arteries  and  drain  the  sigmoid  flexure  of  the 
colon.  The  efferents  carry  the  lymph  to  the  inferior  mesenteric 
nodes. 


J>uc*L 


f 


192. — Lymph  nodes  of  the  pancreas. 


(c)  The  pararectal,  or  superior  hemorrhoidal  nodes  lie  in  contact 
with  the  muscle  coat  of  the  rectum  and  drain  the  upper  part  of  the 
rectum.     The  lymph  then  passes  to  the  inferior  mesenteric  nodes. 

From  the  inferior  mesenteric  nodes  the  lymph  is  carried  by  the 
inferior  mesenteric  trunk  to  the  common  intestinal  trunk. 

The  common  intestinal  trunk  is  the  main  tributary  of  the  cisterna 
chyli  and  receives  the  lymph  from  the  above  organs  through  the 
celiac,  superior  and  inferior  mesenteric  nodes  and  trunks. 

The  lymphatic  drainage  of  the  liver  is  quite  complicated  and 
will  therefore  be  given  special  consideration.  There  are  two  sets 
of  vessels  superficial  and  deep.  The  superficial  vessels  of  the  convex 
surface  drain  in  three  directions.  Those  of  the  left  side  drain  into 
the  paracardial  nodes  of  the  gastric  group;  those  of  the  middle  pass 


THE    LYMPHATICS    OF    THE    THORAX 


26? 


through  the  caval  orifice  of  the  diaphragm  and  empty  into  nodes  at 
the  termination  of  the  inferior  vena  cava;  from  the  right  side  the 
vessels  drain  into  the  celiac  nodes.  In  addition  some  of  the  lymph 
passes  to  the  hepatic  nodes;  some  into  the  inferior  diaphragmatic 
nodes  to  the  internal  mammary  nodes  and  some  to  the  dorsal 
mediastinal  nodes. 

The  superficial  vessels  of  the  visceral  surface  carry  the  lymph 
chiefly  to  the  hepatic  nodes;  some  of  the  lymph  from  the  dorsal  part 
of  this  surface  is  carried  to  the  caval  nodes  above  mentioned. 


Fig.    193. — Ileal  and  ile 


lymph  nodes  and  lymphatic  drainage. 


The  deep  lymphatic  vessels  are  the  ascending  that  accompany  the 
hepatic  veins  and  empty  the  lymph  into  the  caval  nodes,  and  the 
descending  that  emerge  at  the  portal  fissure  and  empty  the  lymph 
into  the  hepatic  nodes. 


THE  THORAX 

The  lymph  nodes  of  the  thorax  comprise  two  wain  sets,  parietal  and 
visceral. 

Parietal.  Visceral. 

1.  Internal  mammary.  1.  Ventral  mediastinal. 

2.  Intercostal  2.  Dorsal  mediastinal. 

3.  Diaphragmatic.  3.  Tracheobronchial. 


266  THE    LYMPH   VASCULAR    SYSTEM 

Parietal. — I.  The  internal  mammary,  or  sternal  nodes  (four  to 
eighteen)  lie  along  the  course  of  the  internal  mammary  artery. 
These  receive  lymph  from  mammary  gland,  the  deeper  structures  of 
the  ventral  thoracic  and  abdominal  walls  (to  umbilicus)  and  dia- 
phragm, from  the  liver  through  the  ventral  diaphragmatic  nodes 
and  from  the  medial  part  of  the  mammary  gland.  The  lymph  then 
passes  through  the  internal  mammary  trunk  that  empties  either  into 
the  subclavian-internal  jugular  vein  junction,  or  upon  the  right 
side  into  the  right  lymphatic  duct,  or  the  right  bronchomediastinal 
trunk,  and  upon  the  left  side  into  the  thoracic  duct. 

2.  The  intercostal  nodes  (L.  intercostales)  lie  at  the  lateral  and 
dorsal  part  of  the  intercostal  spaces.  They  receive  the  lymph  from 
the  deeper  structures  of  the  dorsal  and  lateral  walls  of  the  thorax. 
The  vessels  from  the  lower  four  or  five  intercostal  spaces  usually 
form  a  trunk  on  each  side  that  descends  into  the  abdomen  to  empty 
into  the  cisterna  chyli,  or  into  the  first  part  of  the  thoracic  duct. 
These  are  the  descending  lumbar  trunks.  The  lymph  of  the  left 
upper  intercostal  spaces  drains  into  the  dorsal  mediastinal  nodes, 
or  into  the  thoracic  duct,  while  upon  the  right  side  the  lymph  from 
the  corresponding  spaces  is  emptied  into  the  right  lymphatic  duct. 

3.  The  diaphragmatic  nodes  comprise  three  groups,  (a)  ventral, 
(b)   middle  and  (c)  dorsal. 

(a)  The  ventral  nodes  lie  behind  the  ensiform  cartilage  of  the 
sternum  and  receive  lymph  from  the  convex  surface  of  the  liver 
and  the  ventral  part  of  the  diaphragm.  The  lymph  then  passes 
into  the  internal  mammary  nodes. 

(b)  The  middle  nodes  {right  and  left)  lie  where  the  phrenic  nerves 
enter  the  diaphragm.  Some  of  the  right  nodes  lie  within  the  fibrous 
pericardium.  They  receive  lymph  from  the  middle  of  the  diaphragm 
and  some  from  the  convex  surface  of  the  liver  (and  the  right  nodes). 
The  lymph  then  passes  to  the  dorsal  mediastinal  nodes. 

(c)  The  dorsal  nodes  lies  at  the  dorsal  part  of  the  diaphragm  and 
receive  lymph  from  the  adjacent  regions.  The  lymph  then  passes 
partly  to  the  lateral  aortic  nodes  and  partly  to  the  dorsal  mediastinal 
nodes. 

The  visceral  nodes  are  (1)  ventral  mediastinal,  (2)  dorsal  mediastinal 
and  (3)  tracheobronchial. 

1.  The  ventral  mediastinal  (superior)  nodes  lie  in  front  of  the 
arch  of  the  aorta  in  the  superior  mediastinum.  They  receive  lymph 
from  the  thymus  body  through  the  thymic  nodes  and  the  lymph 
vessels  passing  from  these  nodes  assist  in  forming  the  right  and  left 
bronchomediastinal  trunk. 

2.  The  dorsal  mediastinal  nodes  (eight  to  twelve)  lie  behind  the 
pericardium  near  the  esophagus  and  descending  thoracic  aorta. 
They  receive  lymph  from  the  esophagus,  dorsal  surface  of  the  peri- 


THE    TRACHEOBRONCHIAL    LYMPHATICS 


267 


cardium,  diaphragm  and  the  convex  surface  of  the  liver.  Most 
of  the  lymph  passes  to  the  thoracic  duct  and  the  remainder  to  the 
tracheobronchial  nodes. 

3.  The  tracheobronchial  nodes  comprise  jour  groups,  the  right 
and  left  tracheal  and  the  intertracheobronchial,  the  bronchopulmonary 
and  the  pulmonary. 


Fig.   194. — Tracheobronchial  lymph  nodes. 

(a)  The  right  and  left  tracheal  nodes  lie  upon  the  right  and  left 
sides  of  the  trachea. 

(6)  The  intertracheobronchial  nodes  are  found  in  the  angle  of  the 
bifurcation  of  the  trachea. 

(c)  The  bronchopulmonary  nodes  lie  at  the  hilus  of  the  lung. 

(d)  The  pulmonary  nodes  are  in  the  lungs  in  the  angles  where  the 
bronchial  tube  branches  arise. 

These  nodes  receive  the  lymph  from  the  trachea,  bronchi,  lungs 


268 


THE    LYMPH    VASCULAR    SYSTEM 


and  heart  and  some  from  the  dorsal  mediastinal  nodes.  The  lymph 
passes  into  vessels  that  unite  with  the  vessels  from  the  internal 
mammary  and  ventral  mediastinal  nodes  to  form  the  right  and  left 
bronchomediastinal  trunks.  These  trunks  usually  empty  into  the 
subclavian  and  internal  jugular  vein  junction,  of  their  respective 
sides,  but  may  empty  into  the  right  lymphatic  and  thoracic  ducts, 
respectively. 

THE  SPLEEN  AND  THYMUS  BODY 

Although  the  spleen  and  thymus  are  not  usually  described  under 
the  lymphatic  system  the  fact  that  they  consist  mainly  of  lymphoid 
tissue  seems  to  warrant  their  description  here.  They  are  usually 
described  under  ductless  glands  but  they  are  not  of  epithelial 
structure. 

The  Spleen,  Lien. — The  spleen,  usually  called  a  ductless  gland, 
is  located  deeply  in  the  left  side  of  the  abdominal  cavity.     It  lies 

ycntra-L     bord-er 


PlG.    [95. — The  visceral  surface  of  the  spleen  showing  its  various  areas.      (From  a    photo- 
graph.)    a.  Intermediate  angle;  6,  dorsal  angle;  c,  ventral  angle. 

partly  in  the  epigastric  but  mainly  in  the  left  hypochondriac  regions. 
It  is  about  5  inches  (12.5  cm.)  in  length,  3  inches  (7.5  cm.)  wide  and 
i'4  inches  (3  cm.)  thick.  It  weighs  about  bl2  ounces  (195  grams). 
Its  long  axis  usually  conforms  to  th'e  obliquity  of  the  tenth  rib.  It 
is  irregular  in  shape  but  is  said  to  be  tetrahedral  in  form.  It  is 
soft,  of  a  dark  brown  color  and  very  vascular. 

The  spleen  has  an  apex,  a  base,  two  surfaces  and  three  borders. 
The  apex  is  somewhat  pointed  and  is  about  1J2  inches  (3.75  cm.) 
from  the  midvertebral  line.  The  base  corresponds  to  the  colic  area 
of  the  visceral  surface  and  extends  usually  to  the  midaxillarv  line. 


^ 


THE    SPLEEN  269 

The  parietal,  or  diaphragmatic  surface  is  smooth  and  convex  and 
is  in  contact  with  the  diaphragm.  The  visceral  surface  is  irregular 
and  is  divided  into  three  areas  by  three  ridges.  The  longest  ridge 
starts  below  the  apex  and  extends  nearly  to  the  base.  It  separates 
the  larger,  concave  gastric  area  (above)  from  the  smaller  and  flatter 
renal  area  (below).  On  the  gastric  area  is  seen  the  hilus  where  the 
vessels,  nerve  and  lymph  vessels,  enter  and  leave.  The  triangular 
base,  or  colic  area,  is  the  smallest  and  is  bounded  by  the  medial, 
ventral  and  dorsal  angles. 

The  ventral  border  is  thin  and  notched  and  separates  the  dia- 
phragm a  t  i  c  surface  from  the  r 
gastric  area.  The  dorsal  border  is 
thin  and  separates  the  diaphrag- 
matic surface  from  the  renal  area. 
This  border  corresponds  approxi- 
mately to  the  eleventh  intercostal 
space.  The  inferior  border  sepa- 
rates the  diaphragmatic  surface 
from  the  colic  area. 

The  spleen  is  practically  com- 
pletely invested  by  peritoneum  is 
connected  with  the  stomach  by  a 
fold  of  peritoneum  called  the 
gastrosplenic  omentum.  A  fold  of 
peritoneum  passes  from  the  spleen 
to  the  peritoneum  ventral  to  the 
left  kidney;  this  is  the  licnorenal 
ligament  and  through  this  the 
splenic  artery  reaches  the  organ. 
Another  fold,  the  phrenicocolic 
ligament,  connects  it  with  the 
diaphragm.  _  Fig   1Q0._0utl„ 

The  spleen  is  outlined  upon  the  body  wail. 

body  as  follows:     Three  points  are 

first  determined:  (i)  i}^2  inches  to  the  left  of  the  tenth  thoracic 
spine;  (2)  in  the  eleventh  intercostal  space  on  a  level  with  the  first 
lumbar  spine  and  i  inch  medial  to  the  level  of  the  center  of  the  crest 
of  the  ilium;  (3)  in  the  ninth  interspace  in  the  midaxillary  line.  Join 
the  points  one  and  two  by  a  slightly  curved  line  with  the  convexity 
downward  following  the  eleventh  interspace  (renal  line) ;  join  points 
two  and  three  by  a  curved  line  with  the  convexity  outward  (colic 
line);  then  continue  the  curved  line  from  three  to  the  upper  border 
of  the  ninth  rib  and  follow  this  to  the  scapular  line,  then  horizontally 
across  to  the  upper  border  of  the  tenth  rib  and  then  in  a  sharp  curve 
proceed  to  point  one.     It  must  be  remembered  that  this  gives  the 


270 


THE    LYMPH    VASCULAR    SYSTEM 


anatomic  outline,  but  this  entire  area  does  not  give  dulness  upon 
percussion  as  approximately  the  apical  one-fifth  is  deeply  placed. 

The  artery  that  supplies  the  spleen  is  the  splenic  artery.  The 
splenic  vein  returns  the  blood  to  the  portal  vein.  The  nerves  are 
from  the  splenic  plexus  derived  from  the  solar  plexus  of  the 
sympathetic  system. 

The  Thymus  Body. — The  thymus  body,  or  gland  is  essentially  an 
organ  of  fetal  life  and  early  childhood.  It  is  located  in  the  lower 
cervical  and  upper  thoracic  regions  and  in  the  latter  place  lies  upon 
the  pericardium  and  great  vessels.     It  weighs  about  1  ounce  (28 


Fig.    197. — Ventral 


child  at  birth. 


grams)  at  birth  but  this  is  quite  variable;  it  measures  at  that  time 
about  2  inches  (5  cm.)  in  length,  iH  inches  (3.75  cm.)  in  breadth 
and  ij£  inches  (30  mm.)  in  thickness.  It  is  pinkish  in  color  and 
consists  of  two  unequal  lobes.  After  the  second  year  it  does  not 
grow  in  proportion  to  the  other  organs  of  the  body  and  gradually 
loses  its  lymphoid  structure  and  becomes  more  adipose  in  character. 
Usually  at  puberty  it  is  very  small  though  it  may  be  very  large. 

The  arteries  are  usually  from  the  inferior  thyroid  and  internal 
mammary  arteries  and  its  veins  join  the  corresponding  veins.  The 
nerves  are  derived  from  the  sympathetic  and  vagal  nerves. 


CHAPTER  VI 

THE  RESPIRATORY  SYSTEM 

The  respiratory  system  comprises  the  nasal  cavities,  the  pharynx, 
larynx,  trachea,  bronchi,  lungs  and  pleura. 

THE  NASAL  CAVITIES 

The  nasal  cavities  (Fig.  198),  two  in  number,  extend  from  the  an- 
terior nares  to  the  posterior  nares,  or  choanee.  The  anterior  nares,  or 
nostrils,  lead  into  the  vestibule.  The  lower  part  of  the  vestibule 
is  lined  with  heavy  hairs,  the  vibrism,  that  protect  the  entrance. 
The  upper  part  of  the  vestibule  is  smooth  and  represents  that 
part  of  the  nasal  fossae  lined  by  an  extension  of  the  skin,  beyond 
this  area  a  mucous  membrane  exists.  '  That  part  of  the  nasal  cavity 
above  the  vestibule  is  the  olfactory  portion  as  it  is  concerned  with 
the  sense  of  smell.  This  portion  is  narrow  and  slit-like.  The 
remainder  is  expanded  and  constitutes  the  respiratory  portion. 

The  floor  of  each  cavity  is  formed  by  the  palatal  process  of  the 
maxilla  and  palate  bone  and  the  soft  palate.  The  lateral  wall  is 
formed  by  the  nasal  bone,  frontal  process  of  the  maxilla,  lacrimal 
bone,  labyrinth  of  the  ethmoid  with  its  superior  and  middle  conchal 
processes,  the  vertical  plate  of  the  palate  bone  and  the  medial  surface 
of  the  medial  pterygoid  plate.  The  roof  consists  of  the  nasal  and 
frontal  bones,  the  cribriform  plate  of  the  ethmoid,  the  body  of  the 
sphenoid  and  the  sphenoidal  concha?,  the  sphenoidal  process  of 
the  palate  bone  and  the  ala  of  the  vomer.  The  medial  wall,  or  septum, 
consists  of  the  crests  of  the  palate  bones,  below,  the  vomer,  the  per- 
pendicular plate  of  the  ethmoid,  the  nasal  spine  of  the  frontal  bone, 
and  the  cartilaginous  septum,  in  front.  The  cavity  is  deepest  in 
the  middle  (going  from  front  to  back). 

Upon  the  outer  or  lateral  wall  are  three  projections;  the  inferior 
concha  (the  largest),  the  middle  and  superior  (smallest)  conchal 
processes.  The  space  between  the  floor  and  the  inferior  concha  con- 
stitutes the  inferior  meatus  and  has  the  nasal  duct  opening  into  it. 
The  space  between  the  inferior  concha  and  the  middle  conchal 
processes  is  the  middle  meatus.  As  its  front  extremity  is  the  iufun- 
dibulum  that  leads  into  the  frontal  sinus  and  anterior  ethmoidal 
cells.  In  the  middle  of  the  outer  wall  is  an  opening  that  leads  into 
the   maxillary  sinus.     Between   the   middle  and  superior  conchal 


272 


THE    RESPIRATORY    SYSTEM 


processes  lies  the  superior  meatus  that  communicates  with  the  pos- 
terior ethmoidal  cells.  Above  the  superior  conchal  process  is  a 
small  space  called  the  sphenoethmoidal  recess  that  communicates  with 
the  sphenoidal  sinus. 

The  choanae,  or  posterior  nares,  are  the  openings  by  which  the 
nasal  cavities  communicate  with  the  pharynx.  They  are  larger  than 
the  nostrils. 


Fig.  108. —  Median  sagittal  section  through  the  head  and  neck,  a,  Superior  meatus  of  the 
nose;  6,  middle  meatus  of  the  nose;  c.  inferior  meatus  of  the  nose;  d.  Eustachian  (torus  tuba- 
rius)  cushion;  e,  orifice  of  auditory  tube;  /,  palatoglossal  fold;  g.  tonsil;  h,  palatopharyngeal 
fold;  k,  arycpiglottic  fold;  /,  ventricle  of  the  larynx;  in.  vocal  cord;  K,  vestibule  of  nose. 

The  pharynx  connects  the  nasal  and  oral  cavities  with  the  larynx. 
For  a  description  see  page  290. 

THE  LARYNX 


The  larynx,  or  organ  of  voice  is  situated  at  the  lower  part  of  the 
pharynx  between  the  trachea,  below,  and  the  base  of  the  tongue, 


Male 

Female 

44  mm. 

36  mm. 

43  mm. 

41  mm. 

36  mm. 

26  mm. 

136  mm. 

112   mm. 

THE    LARYNX  273 

above.  It  lies  in  the  upper  and  front  part  of  the  neck  where  it  causes 
a  projection  in  the  midline  that  will  be  described  later.  It  extends 
from  the  lower  border  of  the  third  cervical  vertebra  to  the  lower 
border  of  the  sixth  cervical  vertebra  separated  therefrom  by  the 
pharynx.  Its  position  depends  upon  the  movements  of  the  head  and 
neck  during  deglutition  and  singing.  In  the  fetus  it  lies  at  a  higher 
level  than  in  the  adult.  Up  to  puberty  the  larynx  of  the  male  is  simi- 
lar to  that  of  the  female.  After  this  time  the  increase  in  the  male 
is  greater,  the  cartilages  enlarging,  the  thyreoid  cartilage  becoming 
more  prominent  and  the  glottis  nearly  doubling  its  length.  At  this 
time  the  voice  of  the  male  is  uncertain  and  likely  to  break  at  un- 
expected moments.     The  dimensions  of  the  larynx  are  as  follows: 

Vertical 
Transverse 
Dorsoventral 
Circumference 

The  larynx  at  its  upper  extremity  is  somewhat  triangular  in  out- 
line (base  dorsally  directed)  and  below,  almost  cylindric.  It  consists 
of  nine  cartilages  connected  by  ligaments  and  intrinsic  and  extrinsic 
muscles.     The  cartilages  are: 

Single  Paired 

f  Thyreoid  ( Arytenoid 

j  Cricoid  <  Cuneiform 

I  Epiglottis  [  Cornicula  laryngis 

The  thyreoid  cartilage  (cartilage  thyreoidea)  is  the  largest  and 
consists  of  two  lamella?,  or  ala?.  The  ventral  borders  of  the  als 
meet,  in  their  lower  portions  in  front,  at  an  angle  of  about  90°,  in 
the  male  and  1200  in  the  female.  This  junction  produces  a  promi- 
nence in  the  midline  called  the  prominentia  laryngca,  or  Adam's 
apple,  which  is  more  noticeable  in  the  male  then  in  the  female. 
Above,  these  borders  are  separated  by  a  V-shaped  notch,  the  incisura 
thyreoidea.  The  dorsal  borders  are  thick  and  each  extends  upward  as 
a  long  cylindrical  process,  the  superior  cornu,  and  downward  in  a 
shorter,  heavier  process,  the  inferior  cornu.  The  superior  cornua  are 
connected  to  the  greater  cornua  of  the  hyoid  bone,  while  the  inferior 
cornua  articulate  with  the  lateral  surface  of  the  cricoid  cartilage. 
Upon  the  outer  surface  of  each  ala  is  an  oblique  line  that  divides  this 
surface  into  two  unequal  portions.  The  inner  surface  of  each  is 
smooth  and  to  it  is  attached  the  mucous  membrane  of  the  larynx. 
At  the  angle,  on  this  medial  surface,  are  attached,  from  above 
downward,  the  epiglottis,  the  thyreoepiglottis  ligament,  the  plica 
ventrindaris,  plica  vocalis  and  lastly  the  thyreoepiglottic  and  thy- 
reoarytenoideus  muscles.     To   the  curved   upper  border  is  attached 


274 


THE    RESPIRATOR'S    SYSTEM 


the  tkyreokyoid  membrane  and  to  the  slightly  curved  lower  border  the 
cricothyreoid  membrane. 

The  cricoid  cartilage,  or  signet  ring  {cartilago  cricoidea),  is  smaller 
but  heavier  and  stronger  than  the  thyreoid  cartilage.  It  consists 
of  the  lamina  and  arch.  The  lamina,  nearly  2.5  cm.  in  height,  is 
dorsally  placed  and  lies  between  the  two  alas  of  the  thyreoid  cartilage; 
it  exhibits  a  ridge  in  the  midline  that  gives  attachment  to  the  esoph- 
agus. On  each  side  of  this  line  is  a  shallow  depression  for  attachment 
of  the  cricoarytenoideus  posterior  muscle. 

The  arch  constitutes  the  sides  and  front  of  the  cartilage  and  is 
about  5  to  6  mm.  in  height.  It  gives 
attachment  to  the  cricothyreoideus 
muscle,  in  front,  and  the  inferior  con- 
strictor of  the  pharynx,  behind.  At 
the  junction  of  the  arch  portion  with 
the  lamina  on  each  side  is  a  facet  for 
articulation  with  the  inferior  cornua 
i  of  the  thyreoid  cartilage. 
If '  -  II      The   upper  border  of    the    cricoid 

I  cartilages  gives  attachment  to  the 
cricothyreoid  membrane,  n  front 
and  at  the  sides  and  at  the  side 
also  to  the  cricoarytenoideus  lateralis 
muscle.  The  back  part  presents  a 
facet  on  each  side  of  the  midline  for 
articulation  with  the  arytenoid  carti- 
lages. The  lower  border  of  the  cricoid 
cartilage  is  connected  with  the  first 
ring  of  the  trachea. 

The  epiglottic  cartilage  {cartilago 
cpiglottica)  is  somewhat  leafshaped 
and  is  attached  by  its  lower  smaller 
end  to  the  alar  angle  (upper  part)  by 
the  thyroepiglottic  ligament.  The 
ventral  surface  is  attached  to  the  base  of  the  tongue  by  the  medial 
and  two  lateral  glossoepiglottic  folds.  Two  little  depressions  are  thus 
produced  one  on  each  side  of  the  medial  fold  and  these  are  the 
vallecula.  The  epiglottis  protects  the  glottis  of  the  larynx  during 
deglutition.  From  the  side  of  the  epiglottis  the  arye pi glottic  folds 
extend  backward,  on  each  side,  to  the  arytenoid  cartilage. 

The  arytenoid  cartilages  (cartilagines  arytenoidew),  two  in  number, 
are  small  and  articulate  with  the  upper  part  of  the  cricoid  cartilage. 
Each  has  the  form  of  a  three-sided  pyramid,  having  an  apex,  base 
and  three  small  surfaces.  The  apex  is  pointed  and  is  in  relation  with, 
or  may  be  articulated  with,   the  corniculum  laryngis.     The  base 


THE    LARYNX 


275 


articulates  with  the  cricoid  cartilage.  Two  of  the  basal  angles  are 
important.  The  lateral  angle,  or  muscular  process,  gives  attachment 
to  the  cricoartenoideus  posterior  muscle.  The  ventral  angle,  or 
vocal  process,  gives  attachment  to  the  inferior  thyreoarytenoid 
ligament,  or  the  true  vocal  band.  The  dorsal  surface  gives  attach- 
ment to  the  arytenoideus  muscle.  Upon  the  ventrolateral  surface 
are  attached  the  superior  thyreoarytenoid  ligament,  or  the  false 
vocal  bands  and  the  thyreoartenoideus  muscle.  The  medial  surface 
forms  the  lateral  boundary  of  the  respiratory  glottis. 

The  cornicula  larynges   (cartilagines  corniculata)   are   two  small 
cone-shaped    cartilages    that    surmount    the 
arytenoid  cartilages  at  the  dorsal  end  of  the 
aryepiglottic  folds. 

The  cuneiform  cartilages  (cartilagines 
cunciformes)  are  two,  long,  flat  structures 
located  in  the  aryepiglottic  fold. 

Ligaments. — The  larynx  is  connected  to  the 
hyoid  bone  and  the  trachea  by  the  extrinsic 
ligaments.  The  cartilages  are  connected  to 
one  another  by  the  intrinsic  ligaments.  The 
most  important  of  the  former  is  the  thyreohyoid 
membrane  that  extends  between  the  thyreoid 
cartilage  and  the  hyoid  bone.  Its  variation 
in  thickness  gives  rise  to  several  subsidiary 
ligaments.  Of  the  intrinsic  ligaments  the 
most  important,  from  a  surgical  standpoint, 
is  the  cricothyroid  membrane.  This  extends 
between  the  medial  portion  of  the  arch  of  the 
cricoid  and  the  thyreoid  cartilages.  It  is  not 
of  the  same  thickness  throughout,  thus  giving 
rise  to  subsidiary  ligaments.  It  is  here  that  the  larynx  is  opened 
in  cases  of  obstruction  of  the  glottis. 

The  interior  of  the  larynx  (cavum  laryngis)  is  lined  by  a  mucous 
membrane.  At  the  upper  end  of  the  larynx  is  located  the  superior 
aperture  (aditus  laryngis)  which  is  triangular  in  outline  with  its  base 
at  the  epiglottis  and  its  apex  at  the  apices  of  the  arytenoid  cartilages. 
The  aperture  extends  dorsally  and  downward  and  is  bounded  laterally 
by  the  aryepiglottis  folds.  A  short  distance  beneath  the  aperture 
are  seen  the  vocal  bands.  There  are  two  on  each  side;  the  superior 
fold  is  called  the  false  vocal  band,  or  plica  ventricularis  and  contains 
the  superior  thyreoarytenoid  ligament.  The  inferior  fold  is  the  true 
vocal  band,  or  plica  vocalis  and  contains  the  inferior  thyreoarytenoid 
ligament.  On  each  side  of  the  larynx  between  each  pair  of  folds  is  a 
depression  or  pouch  called  the  ventricle  of  the  larynx  (ventriculus 
laryngis).     An  extension  upward  and  forward  from  each  ventricle, 


Interior  of  the 
from  the  left. 
entricularis;  b, 
plica  vocalis. 


276 


THE    RESPIRATORY    SYSTEM 


between  the  false  vocal  band  and  the  thyreoid  cartilage  constitutes 
the  saccule  (appendix  ventriculi  laryngis).  That  part  of  the  cavity 
between  the  true  bands  and  the  aperture  is  the  vestibule  of  the  larynx. 
The  rima  glottidis  is  the  narrow  dorsoventral  slit  between  the 
true  vocal  folds.  In  the  male  this  measures  about  23  mm.  in  length 
and  in  the  female  about  16  to  20  mm.  The  ventral  three-fifths 
constitutes  the  vocal  portion  (pars  intermembranacea)  and  the  dorsal 
two-fifths  is  the  respiratory  part  (pars  intercartilaginea) .  The  shape 
of  each  portion  depends  upon  the  movements  of  the  vocal  folds 

during  respiration  and  phona- 
tion.  The  lower  portion  of  the 
cavity  of  the  larynx  constitutes 
the  body  and  this  is  nearly 
cylindrical  in  shape. 

The  muscles  of  the  larynx 
are  intrinsic  and  extrinsic.  The 
former  serve  to  move  the  larynx 
up  and  down  while  the  latter  are 
connected  with  the  processes  of 
phonation  and  respiration.  The 
intrinsic  muscles  are  as  follows: 

Mm.   cricothyreoidei  (two)  render 

the  cords  tense. 
Mm.      thyreoarytenoidei        (two) 

relax  the  cords. 
Mm.      cricoarytenoidci      posticuj 

(two)  open  the  glottis. 
Mm.      cricoarytenoidei       lateralis 

(two)  close  the  glottis. 
M.      arytenoideus  (one). 

THE  TRACHEA  AND  BRONCHI 

The  trachea  or  windpipe,  extends  from  the  lower  border  of  the 
sixth  cervical  vertebra  to  the  upper  border  of  the  fifth  thoracic  verte- 
bra where  it  divides  into  right  and  left  stem  bronchi.  It  is  about  4}$ 
inches  (11  cm.)  long  in  the  male  and  from  3^  to  4  inches  (8.75  cm.) 
in  length  in  the  female.  It  consists  of  two  portions,  cervical  and 
thoracic.  It  is  nearly  cylindrical  in  shape  with  the  dorsal  part 
flattened.  Its  caliber  in  the  living  is  12.5  mm.  transversely  and  11 
mm.  dorsoventrally;  in  the  cadaver  it  measures  from  19  to  25  mm. 
transversely.  Its  caliber  is  slightly  greater  in  the  middle  than  at 
either  end.  It  is  composed  of  fifteen  to  twenty  C-shaped  plates  of 
cartilage  separated  from  one  another  by  white  fibrous  tissue  and 
mucous  membrane. 

The  bronchi  are  two  in  number,  right  and  left.     That  part  to  the 


THE    LUNGS    AND    PLEUR.-E  277 

first  branch  constitutes  the  stem  bronchus  and  the  divisions  are  the 
branch  bronchi. 

The  right  stem  bronchus  is  about  1  inch  (2.5  cm.)  in  length,  makes 
an  angle  of  about  250  with  the  midline  of  bifurcation  and  enters  the 
right  lung  at  the  level  of  the  fifth  thoracic  vertebra.  It  has  a  greater 
diameter  than  the  left  and  gives  off  three  branches,  one  for  each  lobe 
of  the  right  lung.     The  first  branch  is  called  the  eparterial  bronchus. 

The  left  bronchus  is  about  2  inches  (5  cm.)  in  length  and  makes  an 
angle  of  about  460  with  the  midline  of  bifurcation.  It  enters  the 
lung  at  the  level  of  the  sixth  thoracic  vertebra.  It  gives  off  but  two 
branch  bronchi,  one  for  each  of  the  two  lobes  of  the  left  lung.  The 
first  branch  is  called  the  hyparterial  bronchus. 

THE  LUNGS  AND  PLEURA 

The  lungs  (puhnoncs)  two  in  number,  are  the  real  organs  of  respira- 
tion. They  occupy  the  bulk  of  the  thoracic  cavity  and  extend  into 
the  neck;  each  lies  in  a  completely  closed  serous  sac,  or  space. 
The  right  lung  weighs  about  22  ounces  and  the  left  lung  about  20 
ounces  in  the  cadaver.  In  the  bloodless  condition,  after  electro- 
cution, the  weights  are  8l2  ounces  and  71;  ounces,  respectively. 
Each  lung  is  smooth  and  glistening  and,  at  birth,  of  a  pinkish  color. 
In  adult  life  it  is  usually  mottled,  becoming  darker  as  age  advances. 
Each  lung  is  somewhat  conical  in  shape  and  presents  an  apex,  a 
base,  two  surfaces  and  three  borders. 

The  apex  is  blunt  and  projects  out  of  the  thoracic  cavity  into 
the  root  of  the  neck  to  the  extent  of  about  1  inch  above  the  first 
rib.  The  medial  and  ventral  part  is  grooved  by  the  subclavian 
artery. 

The  base,  or  diaphragmatic  surface  is  smooth,  semilunar  in  shape 
and  concave  fitting  upon  the  dome  of  the  diaphragm  on  each  side. 
The  right  dome  of  the  diaphragm  ascends  higher  than  does  the  left 
so  that  the  concavity  is  deeper  in  the  right  lung. 

The  costal  surface  is  smooth  and  convex  and  may  show  grooves, 
corresponding  to  the  ribs,  in  specimens  hardened  in  situ.  It  is  the 
most  extensive  surface. 

The  mediastinal  surface  is  triangular  in  shape  and  concave  for  the 
accommodation  of  the  heart  and  pericardium.  A  special  part  where 
the  vessels,  nerves,  lymph  vessels  and  bronchi  enter  and  leave  is 
noted  and  this  is  the  root,  or  hilus.  This  surface  differs  in  the  two 
lungs. 

In  the  left  lung  the  concavity  is  deeper.  The  root  (radix  pul- 
monis) occupies  a  position  a  little  behind  and  above  the  middle  of 
the  surface.  It  is  outlined  by  the  reflections  of  the  pleura  and  con- 
sists of  the  bronchus  and  its  branches,  the  pulmonary  artery  and 


278  THE    RESPIRATORY    SYSTEM 

veins,  the  bronchial  artery  and  vein,  nerves  and  lymphatics.  In  the 
root  the  order  of  the  chief  structures  is,  from  above  downward,  artery, 
bronchus,  vein.  At  the  lower  part  of  the  root  the  two  layers  of 
pleura  that  bound  the  root  come  together,  continue  to  the  base  and 
extend  from  the  lung  to  the  mediastinal  pleura  as  a  band  called 
ligamentum  latum  pulmonis.  Above  the  root  is  seen  the  aortic  groove 
caused  by  the  arch  of  the  aorta;  from  this  groove  the  subclavian 
groove  extends  upon  the  apex;  ventral  to  this  groove  is  seen  another 
made  by  the  left  innominate  vein.  The  aortic  groove  is  seen  extend- 
ing downward  along  the  dorsal  part  of  this  surface. 

In  the  right  lung  the  root  has  the  same  general  position,  appear- 
ance and  structures.     The  order,  however  is  different;  from  above 


Fig.  202. — Medial  surface  of  the  luntrs.  A.  Right  lung;  B.  left  lung,  a.  Groove  for  the 
right  innominate  vein;  b,  groove  for  the  innominate  artery;  c  groove  for  left  subclavian 
artery;  d,  groove  for  left  innominate  vein;  e,  e,  lig.  latum  pulmonis;  /,  /,  pulmonary  arteries; 
g.  g.  bronchi;  h,  h,  pulmonary  veins. 

downward  we  find  bronchus,  artery  and  vein.  The  ligamentum 
latum  pulmonis  is  present.  Above  the  root  is  a  deep  groove  that  is 
formed  by  the  vena  azygos  major  as  it  hooks  over  the  root  to  empty 
into  the  superior  vena  cava;  above  and  passing  outward  is  a  deep 
groove  for  the  superior  vena  cava  and  right  innominate  vein; 
behind  the  latter  the  innominate  artery  may  form  a  groove.  At  the 
dorsal  part  of  this  surface  may  be  a  long  groove  formed  by  the 
esophagus. 

The  borders  are  ventral,  dorsal  and  inferior,  or  basal.  The  ventral 
border  is  thin  and  sharp  and  upon  the  left  lung  presents  a  notch 
called  the  incisura  cardiaca.     The  dorsal  border  is  rounded,   thick 


THE    PLEURAL    REFLECTIONS  279 

and  rests  in  the  deep  concavity  at  the  side  of  the  vertebral  column. 
The  basal  border  is  sharp  and  thin,  separates  the  base  from  the  other 
surfaces  and  extends  into  the  costophrenic  sinus. 

The  right  lung  contains  three  lobes,  the  upper,  middle  and  lower 
and  two  fissures  while  the  left  lung  presents  two  lobes,  upper  and  lower 
separated  by  the  one  fissure.  The  lines  for  the  fissures  will  be  given 
later. 

As  previously  mentioned  each  lung  is  in  a  closed  serous  cavity  the 
pleural  cavity.  The  serous  membrane  bounding  this  space  is  called 
the  pleura.  The  pleura  is  divided  into  portions  according  to  parts 
invested,  as  visceral,  that  investing  the  lung,  and  parietal,  that 
attached  to  the  ribs,  diaphragm  and  pericardium,  thus  bounding 
each  pleural  cavity.  The  visceral  pleura  invests  the  lungs  except  at 
the  root  where  the  layers  are  separated  by  the  structures  entering 
and  leaving  the  lung.  At  the  lower  limit  of  the  root  the  layers 
approximate  and  constitute  the  ligamentum  latum  pulmonis.  The 
visceral  pleura  extends  into  the  fissures  and  completely  separates 
the  lobes  from  each  other. 

The  parietal  pleura  consists  of  several  subdivisions:  that  covering 
the  inner  surfaces  of  the  ribs,  cartilages  and  intercostal  muscles 
and  membranes  constitutes  the  costal  pleura;  that  upon  the  dia- 
phragm is  the  diaphragmatic  pleura;  that  toward  the  midline  upon 
the  pericardium  constitutes  the  mediastinal  pleura,  while  that  portion 
that  covers  the  apex  of  the  lung  in  the  neck  is  the  cervical  pleura. 
These  pleural  reflections  forming  a  closed  sac  constitute  a  continuous 
layer  of  endothelium  and  it  is  possible  to  start  at  any  point  and 
return  after  passing  over  the  various  divisions  without  an  interrup- 
tion in  the  serous  membrane.  The  surface  is  constantly  kept  moist 
with  lymph  so  as  to  prevent  friction. 

As  will  be  seen  later  the  lungs  do  not  extend  down  completely 
into  the  cleft  between  the  diaphragm  and  body  wall;  this  serous 
space  unoccupied  by  lung  is  called  the  costophrenic  sinus.  It  is 
deepest  in  the  midaxillary  line. 

The  outline  of  the  pleura  upon  the  body  wall  is  as  follows:  From 
a  point  '2  to  1  inch  (1  to  2.5  cm.)  above  the  clavicle  over 
the  sternal  end  of  the  first  rib,  draw  a  line  to  the  midsternal  line  to 
pass  under  the  sternoclavicular  articulation.  On  the  right  side 
continue  this  line  down  to  the  level  of  the  sixth  ehondrosternal  junc- 
tion, then  obliquely  outward  to  the  tenth  rib,  or  interspace  on  the 
midaxillary  line  and  then  horizontally  across  to  a  point  between 
the  spine  of  the  twelfth  thoracic  vertebra  and  the  transverse  process 
of  the  first  lumbar  vertebra.  From  this  point  carry  a  line  verti- 
cally to  the  upper  border  of  the  third  thoracic  vertebra  and  then 
arch  across  to  the  apex  point.  The  right  apex  is  about \  ■>  inch  higher 
than  the  left  apex. 


28o 


THE    RESPIRATOR'S    SYSTEM 


On  the  left  side  where  the  apex  line  reaches  the  midsternal  line 
continue  down  to  the  level  of  the  junction  of  the  fourth  cartilage 


Fig.    203. — Outline  of  pleura?  aid  lun^s  upon   the  ventral  thoracic  wall. 
i/»  !»!  a  photograph.)      A,  Area  of  superficial  cardiac  dullness. 


Fu;.   J04.— Outline  of  pleura  and  lungs  upon  the  dorsal  thoracic  wall.     (From  a  photograph.) 

with  the  sternum  then  turn  out  to  the  edge  of  the  sternum  and  down 
to  the  level  of  the  sixth  chondrosternal  junction,  then  outward 
to  the  upper  border  of  the  tenth  rib  in  the  midaxillary  line,  thence 


THE    PLEURAL    REFLECTIONS  26l 

across  to  a  point  midway  between  the  twelfth  thoracic  spine  and 
the  transverse  process  of  the  first  lumbar  vertebra.  Then  continue 
vertically  upward  to  the  level  of  the  upper  border  of  the  third 
thoracic  vertebra  and  then  arch  across  to  the  apex  point. 

To  outline  the  lungs  draw  a  line  from  the  apex  point  to  the  mid- 
sternal  line  passing  beneath  the  sternoclavicular  articulation  and 
just  within  the  pleural  line.  On  the  right  side  the  edge  of  the  lung 
follows  the  pleural  line  to  the  sixth  chondrosternal  junction,  then 
passes  obliquely  downward  and  outward  to  cross  the  eighth  rib 
on  the  midaxillary  line,  then  horizontally  across  to  the  level  of  the 
tenth  thoracic  spine  and  up  along  the  vertical  pleural  line  to  the 
apex  point.  On  the  left  side  follow  the  pleural  line  from  the  apex 
point  to  the  midsternal  line,  then  down  parallel  to  the  pleural 
reflection  to  the  level  of  the  fourth  chondrosternal  junction,  then 
outward  in  a  curved  line  so  that  the  deviation  is  about  5  cm.  from 
the  midsternal  line  in  the  fourth  interspace;  then  curve  toward  the 
sternum  for  about  2.5  cm.  thence  downward  and  outward  to  cross 
the  eighth  rib  in  the  midaxillary  line,  across  to  the  level  of  the  tenth 
thoracic  spine,  up  parallel  to  the  pleural  line  to  the  apex  point. 

To  outline  the  main  fissure  start  on  the  back  at  the  level  of  the 
transverse  process  of  the  third  thoracic  vertebra,  pass  obliquely 
down  so  as  to  reach  the  lower  border  of  the  lung  at  the  parasternal 
line.  This  separates  the  upper  from  the  lower  lobe.  On  the  right 
side  the  intermediate  fissure  starts  from  the  main  fissure  at  the 
midaxillary  line  and  crosses  the  front  of  the  thorax  practically  hori- 
zontally to  the  junction  of  the  fourth  cartilage  with  the  sternum. 
This  fissure  separates  the  upper  from  the  middle  lobe. 


CHAPTER  VII 


THE  ALIMENTARY  TRACT  (APPARATUS  DIGESTORIUS) 

The  alimentary  tract  is  a  tube-like  structure  about  30  feet  in  length 
extending  from  the  lips  to  the  anus.  Here  the  food  is  mechanically 
and  chemically  treated  (digested)  so  that  it  is  capable  of  absorp- 
tion. The  caudal  portion  of  the  apparatus  receives  and  expels  the 
undigestible  portions  of  the  food.  In  addition  to  the  tube  are 
various  organs  that  lie  in  the  wall  of  the  tube  or  lie  outside  and  are 
connected  to  the  tract;  these  are  the  accessory  organs.  All  of  the 
tract  caudal  to  the  pharynx  is  called  the  tubus  digestorius.  The 
parts  of  the  alimentary  tract  are  as  follows: 


f  Aperture 
Mouth      \  Vestibule 

I  Oral  cavity  proper 

Pharynx 

Esophagus 

Stomach 


Small  intestine 


C  Duodenum 
\  Jejunum 
[  Ileum 


Accessory  organs 
(■  Teeth 

Gums 
\  Tongue 

Salivary  glands 
I  Tonsils'  (?) 


/  Liver 
I  Pancreas 


Large  intestine 


Colon 


Cecum  and  appendix 
ascending 
transverse 
descending 
I  sigmoid 

Rectum 

Anal  canal 

Anus 


THE  MOUTH 

The  mouth  comprises  the  aperture,  vestibule  and  oral  cavity  proper 
and  here  are  found  the  accessory  organs,  the  teeth,  tongue,  gums  and 
oral  salivary  glands. 

The  aperture  (rima  oris)  is  the  narrow  slit  between  the  lips  (labia 
oris).  It  is  placed  transversely  and  is  bow-shaped.  It  is  about  2 
inches  (5  cm.)  in  length  and  extends  from  the  first  premolar  of  one 
side  to  the  corresponding  premolar  of  the  opposite  side. 


THE   VESTIBULE 


283 


The  vestibule  (vestibulum  oris)  in  a  state  of  rest  is  a  narrow,  slit- 
like cavity  that  lies  between  the  lips  and  cheeks  (buccal)  externally, 


■Fig.   20s. — A  diagram  of  th 


ntary  tract. 


and  the  teeth  and  gums,  internally.     The  lips  bounding  the  aperture 
and   vestibule  consist   of  skin  externally  and  mucous  membrane 


THE    ALIMENTARY    TRACT 


internally.  Between  these  lie  the  muscles,  fat  and  white  fibrous 
tissue  supporting  blood-vessels,  nerves  and  lymphatics.  In  the 
mucous-membrane  side  lie  numerous  small  labial  salivary  glands. 
Internally,  each  lip  is  connected  to  the  gum  by  a  delicate  fold  of 
mucous  membrane,  the  frenum;  that  of  the  upper  lip  is  the  larger. 

The  cheeks  (buccal)  consist  of  skin  externally  and  mucous  mem- 
brane internally.  Between  these  lie  the  muscles,  fat  and  white 
fibrous  tissue  and  the  buccal  salivary  glands,  besides  blood-vessels, 
nerves  and  lymphatics.  In  the  infant,  in  the  superficial  fascia,  is 
an  encapsulated  mass  of  fat  called  the  corpus  adiposum  bucccr,  or 
sucking  pad.  It  is  of  great  importance  as  it  strengthens  the  cheek 
during  nursing.     In  the  adult  it  is  less  prominent. 

The  gums  ( gingiva)  constitute  the 
mucous  membrane  covering  the 
alveolar  portions  of  the  maxillae  and 
mandible.  They  consist  of  a  firm 
red  tissue  about  i  or  2  mm.  thick. 
They  are  quite  vascular,  are  firmly 
attached  to  the  periosteum  and  ex- 
tend about  the  base  of  the  crown  of 
each  tooth  in  the  form  of  a  collar. 

The  vestibule  communicates  with 
the  mouth  cavity  by  the  small  spaces 
between  the  teeth  and  a  large  space 
behind  the  last  molar  teeth.  On  the 
inside  of  the  cheek,  opposite  to  the 
second  upper  molar  tooth,  is  a  papilla 
where  the  parotid  duct  empties  its 
secretion  into  this  vestibule. 

The  oral  cavity  proper  is  bounded 
above  by  the  palate,  below  by  the 
tongue  and  floor,  or  sublingual  region 
and  laterally  and  in  front  by  the  teeth  and  gums.  The  dorsal  wall 
is  wanting,  constituting  the  communication  with  the  pharynx. 

The  palate  (palatum)  consists  of  two  portions,  hard  and  soft. 
The  hard  palate  (palatum  durum)  constitutes  the  ventral  two-thirds 
of  the  roof  and  is  nearly  horizontal  in  direction.  It  is  formed  by 
the  palatal  processes  of  the  maxillae  and  the  palate  bones  and  is 
covered  by  a  mucous  membrane  and  shows  a  ridge  in  the  midline 
called  the  raphe;  some  transverse  folds,  the  ruga:  [plica  palatina-) 
are  seen.     The  soft  tissues  contain  the  palatal  salivary  glands. 

The  soft  palate  {palatum  molle)  constitutes  the  dorsal  one-third  . 
of  the  roof  and  it  slopes  downward  (caudad)  and  backward.     The 
dorsal  free  edge  consists  of   two  lateral  arches  produced  by   the 
downward  projecting,  cone-like  process  of  the  middle  of  the  soft 


Fig.  206. — Mouthopened.  ,1.1'alat 
oglossal  fold;  B.  palatopharyngeal  fold 
c,  tonsil;  D,  uvula. 


THE    TEETH  285 

palate  called  the  uvula.  This  part  varies  in  length  in  different 
individuals.  The  ventral  edge  of  the  soft  palate  is  attached  to  the 
hard  palate  the  upper  and  lower  surfaces  are  covered  by  mucous 
membranes  that  become  continuous  at  the  free  edge.  Between 
these  mucous  membranes  lie  the  palatal  aponeurosis  (attached  to  the 
hard  palate)  and  the  muscles  of  the  palate  (in  the  posterior  two- 
thirds  of  the  soft  palate).  Extending  downward  from  the  palate, 
are  two  folds  on  each  side,  the  arches,  that  will  be  described  later. 

The  muscles  of  the  soft  palate  are  the  mm.  tensor  veil  palatini, 
levator  veil  palatini,  glossopalatinus,  pkaryngopalatinus  and  uvula,  all 
paired. 

The  blood  supply  of  the  palate  is  from  the  descending  palatine 
branch  of  the  internal  maxillary  artery,  the  ascending  palatine 
artery  and  branches  from  the  ascending  pharyngeal  and  dorsalis 
lingua?  arteries. 

The  sensor  nerves  are  from  the  sphenopalatine  ganglion.  These 
are  the  anterior,  middle  and  posterior  palatine  nerves;  the  motor 
nerves  for  all  muscles,  except  the  tensor  veli  palatini,  come  from  the 
spinal  accessory  nerve  through  the  pharyngeal  plexus.  The  tensor 
veli  palatini  is  supplied  by  the  motor  portion  of  the  trigeminal  nerve 
through  the  otic  ganglion. 

The  floor  of  the  mouth  consists  of  the  tongue  and  the  sublingual 
region.  The  sublingual  region,  or  true  floor,  consists  of  the  tissues 
between  the  anterior  part  of  the  base  of  the  tongue  and  the  mandible. 
Connecting  the  tongue  to  the  floor  in  the  midline  is  a  small  fold  of 
mucous  membrane,  the  frenulum  lingua;.  On  each  side  of  this  fold 
is  a  little  papilla  (caruncula  sublingualis)  in  which  is  the  orifice  of 
the  submaxillary  duct. 

Extending  from  the  papilla  on  each  side  is  a  fold  of  mucous  mem- 
brane, the  plica  sublingualis,  in  which  are  seen  numerous  openings 
representing  the  orifices  of  the  sublingual  ducts. 

The  teeth  (denies)  are  the  organs  of  mastication.  During  life 
there  are  two  sets,  temporary  and  permanent.  The  temporary,  or 
deciduous  teeth  (denies  decidui),  are  twenty  in  number  and  begin 
to  erupt  about  the  sixth  or  seventh  month  and  are  all  present  at 
about  the  twenty-fourth  to  the  thirtieth  month.  In  each  jaw  are 
found  central  incisors  (two),  lateral  incisors  (two),  canines  (two)  and 
molars  (four).  In  the  permanent  set  (denies  permanentes)  there  are 
thirty-two  teeth.  In  each  jaw  are  found  two  central  incisors,  two 
lateral  incisors,  two  canines,  four  premolars  and  six  molars.  These 
teeth  begin  to  erupt  at  about  the  sixth  year  and  all  are  present  at 
about  the  twenty-first  to  the  twenty-fifth  year. 

Each  tooth  consists  of  a  central  cavity  (cavum  dentis)  surrounded 
by  the  dentin  (substantia  cburnea)  that  gives  the  form  to  and  consti- 
tutes the  bulk  of  the  tooth.     That  portion  of  the  tooth  projecting 


286 


THE    ALIMENTARY    TRACT 


beyond  the  line  of  the  alveolar  socket  of  the  jaw  is  the  crown  (corona 
dentis)  and  is  covered  by  the  enamel  (substantia  adamantina);  that 
portion  covered  by  the  gum  is  the  neck  (collum  dentis)  while  that  part 


\   »     —Enamel 


Fig.   20S. — Mandible  with  the  permanent  teeth 
canine;  D.  premolar 


1,  Ce 
,  mola 


within  the  alveolar  process  constitutes  the  root  {radix  dentis).  The 
root  is  held  in  the  alveolar  socket  by  the  peridental  membrane  (peri- 
osteum aheolare).  At  the  apex  of  the  root  is  an  opening  (foramen 
apicis)  that  leads  into  the  root  canal  (canalis  radicis)  that  terminates 


THE   TONGUE  287 

in  the  pulp  cavity  (cavum  dent  is).  The  latter  is  occupied  by  the 
tooth  pulp  (pulpa  dentis).  The  part  of  the  tooth  that  opposes  that 
of  the  other  jaw  is  called  the  fades  masticatoria. 

The  incisors  (denies  incisivi)  are  chisel-like  teeth  and  those  of 
the  upper  jaw  are  larger  and  stronger  than  those  of  the  mandible. 
The  root  of  each  tooth  is  flattened  laterally. 

The  canines  (denies  canini)  are  pointed,  or  conical  in  shape  and 
are  stronger  than  the  incisors.  They  represent  the  holding  and 
tearing  teeth  of  the  lower  animals.  The  rcot  of  each  is  nearly  conical 
and  longer  than  that  of  the  incisor  tooth. 

The  premolars  (denies  premolares)  exhibit  two  little  projections 
or  cusps  upon  the  crown  the  latter  being  more  massive  than  in  the 
preceding  teeth.  The  root  of  each  tooth  is  usually  single  and 
flattened  from  side  to  side. 

The  molars  (denies  molares)  are  the  most  massive  teeth;  the  crowns 
are  cuboidal  and  the  cusps  three  to  five  in  number.  Each  upper 
tooth  possesses  three  roots  while  each  lower  but  two  roots.  The 
third  molar,  or  wisdom  tooth,  is  called  the  dens  serotinus. 

In  the  normal  condition  the  teeth  form  an  arch  in  each  jaw  the 
dental  arch  (arcus  dental  is).  The  upper  is  slightly  the  larger  and 
therefore  slightly  overlaps  the  lower  arch. 

The  tongue  (lingua)  is  the  most  mobile  organ  in  the  body.  It 
has  the  following  important  functions:  Mastication,  insalivation, 
deglutition,  taste  and  speech.  In  order  to  get  the  proper  shape  and 
dimensions  of  the  tongue  it  must  be  hardened  in  situ.  It  is  about  9 
cm.  ($li  inches)  in  length  and  lies  in  the  oral  cavity  proper  and 
oropharynx.  It  consists  of  apex,  base,  dorsum,  inferior  surface  and 
margin. 

The  apex,  or  tip  (apex  lingua)  is  the  free  extremity  and  is  usually 
narrow  and  thin,  resting  against  the  incisor  teeth. 

The  base,  or  root  (radix  lingua)  is  the  attached  portion  and  is 
broad  and  massive.  It  is  directed  downward  (caudad)  and  back- 
ward and  is  attached  to  the  hyoid  bone,  mandible  and  floor  of  the 
mouth. 

The  dorsum  (dorsum  lingua:)  consists  of  two  parts,  the  anterior, 
or  apical  two-thirds  and  posterior,  or  basal  one-third.  The  apical 
two-thirds,  or  oral  part,  is  nearly  horizontal  and  slightly  arched  from 
before  backward  and  from  side  to  side.  It  may  show  a  slight 
median,  longitudinal  groove  (sulcus  mediants)  that  ends  posteriorly 
in  the  foramen  cecum.  The  apical  two-thirds  is  separated  from  the 
basal  one-third  by  a  slight  V-shaped  groove,  the  sulcus  lerminalis, 
the  apex  of  which  is  the  foramen  cecum.  In  front  of  the  sulcus  is  a 
V-shaped  collection  of  papilla,  eight  to  ten  in  number,  below  the 
surface,  called  the  vallate  papilla:.  These  contain  the  taste-buds. 
Scattered   over   the   dorsum   are   smaller,   conical  projections,   the 


THE    ALIMENTARY    TRACT 


tUUfonn  papilla';  a  third  variety,  the  fungiform  papilla  are  less 
numerous  than  the  filliform  and  are  found  chiefly  at  the  sides  and 
apex. 

The  basal  one-third,  or  pharyngeal  part  of  the  tongue,  is  nearly 
vertical  in  direction.  Papilla?  are  not  found  here  but  rounded  ele- 
vations, that  represent  masses  of  lymphoid  tissue  below  the  mucosa, 
are  present.     These  constitute  the  lingual  tonsil  (tonsilla  lingual  is). 

The  dorsum  of  the  base  is  connected  to  the  epiglottis  by  three  folds, 
two  lateral  (plica;  pharyngoepiglotticm)  and  one  median  (plica  glosso- 
epiglottica),  the  glossoepiglottic  folds.  Between  the  median  and  each 
lateral  fold  a  little  fossa  is  formed,  the  vallecula. 

The  inferior  surface  (fascies  inferior)  of  the  tongue  is  not  extensive. 
Here  is  seen  a  part  of  the  frenulum  lingua?  and  upon  each  side  of 


Fie.  209. — Do 


ith  the  epiglottis 


this  a  slight  fold  of  mucous  membrane,  the  plica  fimbriata.  Near 
the  tip  there  may  be  a  slight  elevation  that  indicates  the  presence 
of  the  apical  gland. 

The  margin  (margo  lateralis)  of  the  tongue  is  free  in  front  of  the 
anterior  arches  of  the  fauces  and  separates  the  dorsum  from  the 
inferior  surface.  The  tongue  is  covered  by  a  mucous  membrane. 
The  bulk  of  the  organ  consists  of  voluntary  striated  muscle  tissue. 
The  muscles  comprise  two  sets,  the  intrinsic  and  the  extrinsic. 
The  intrinsic  muscles  are  the  superior  and  inferior  longitudinal, 
the  transverse  and  the  vertical  lingual  muscles.  The  extrinsic  are 
the  hyoglossus,  genioglossus,  glossopalatinus,  styloglossus  and  choudro- 
glossus.  In  the  tongue  are  numerous  small  glands,  the  lingual 
salivary  glands  (gland nice  linguales). 


THE  ORAL  SALIVARY  GLANDS 


289 


The  arteries  are  the  lingual,  external  maxillary  and  ascending 
pharyngeal.  The  nerves  are  the  hypoglossal,  glossopharyngeal, 
chorda  tympani,  the  lingual  branch  of  the  mandibular  division  of  the 
trigeminal  and  the  internal  laryngeal  branch  of  the  vagus. 

The  principal  oral  salivary  glands  {glandule  salivares)  are  six 
in  number,  two  parotid,  two  submaxillary  and  two  sublingual. 

The  parotid  gland  (glandula  parotis)  is  the  largest  and  weighs  from 
20  to  30  grams.  It  lies  upon  the  side  of  the  face  and  chiefly  in  front 
of  the  ear.  It  is  bounded  above  by  the  zygomatic  arch,  below  by  the 
angle  of  the  mandible  and  a  line  extending  back  to  the  mastoid 


Fig.  210. — The  oral  salivary  glands  in  their  normal  positions. 

process.  In  front  it  extends  a  little  distance  over  the  masseter 
muscle,  behind  to  the  external  auditory  canal  and  sternomastoid 
muscle.  The  deepest  and  thickest  part  is  wedge-shaped  and  in 
close  relation  with  the  great  vessels  of  the  neck.  This  constitutes 
the  processus  retromandibularis  and  occupies  the  so-called  parotid 
fossa.  Within  the  gland  are  important  vessels  and  the  facial  nerve 
and  its  branches. 

The  parotid  duct  {ductus  parotideus)  extends  from  the  upper 
anterior  part  of  the  gland,  is  5  to  6  cm.  in  length  and  empties  into 
the  vestibule  opposite  the  second  upper  molar  tooth.     This  duct 


290  THE    ALIMENTARY    TRACT 

corresponds  approximately  to  the  middle  third  of  a  line  drawn  from 
the  lower  margin  of  the  external  auditory  meatus  to  the  middle  of 
the  upper  lip. 

The  blood  supply  of  the  parotid  gland  consists  of  branches  from 
the  external  carotid  artery  and  other  arteries  in  relation  with  the 
gland. 

The  nerves  are  from  the  great  auricular,  facial,  auriculotemporal 
(from  otic  ganglion)  nerves  and  the  external  carotid  plexus  of  the 
sympathetic  system  (the  latter  are  chiefly  vasomotor). 

The  submaxillary  gland  (glandula  submaxillaris)  weighs  8  to  10 
grams  and  is  located  under  the  middle  of  the  body  of  the  mandible 
in  the  submaxillary  triangle.  A  process  of  the  gland  usually  extend 
forward  and  medially. 

The  submaxillary  duct  (ductus  submaxillaris)  is  about  5  cm.  long 
and  empties  into  the  oral  cavity  at  the  side  of  the  frenum  lingua 
at  the  apex  of  the  caruncula  sublingualis. 

The  submaxillary  gland  receives  its  blood  supply  from  the  external 
maxillary  artery.  The  nerves  are  from  the  chorda  tympani  and  the 
lingual  nerves,  from  the  submaxillary  ganglion  and  the  external 
maxillary  plexus. 

The  sublingual  gland  (glandula  sublingualis,)  3  to  4  grams  in 
weight,  is  a  collection  of  glands  in  the  floor  of  the  oral  cavity  upon 
each  side  of  the  frenum.  They  form  a  mass  from  35  to  45  mm.  in 
length.  The  ducts  (ducti  sublinguales  minor es)  may  be  fifteen  to 
twenty  in  number  upon  each  side  and  empty  into  the  oral  cavity  on 
the  plica  sublingualis. 

The  blood  supply  of  the  sublingual  glands  consists  of  the  sublingual 
(from  the  lingual),  the  submental  (from  the  external  maxillary) 
arteries.  The  nerves  are  derived  from  the  lingual  and  chorda  tym- 
pani nerves  through  the  submaxillary  ganglion  and  from  the 
external  maxillary  plexus. 

In  the  mouth  cavity  the  processes  of  digestion  that  take  place 
are  mastication  and  insalivation. 

The  pharynx  is  somewhat  funnel-shaped  but  flattened  from  before 
backward.  It  extends  from  the  base  of  the  skull  to  the  sixth  cervical 
vertebra,  behind,  and  the  cricoid  cartilage,  in  front.  It  is  5  to  5H 
inches  (12.5  to  14  cm.)  in  length  and  widest  in  the  upper  part  behind 
the  orifices  of  the  auditory  tubes.  The  nasopharynx  is  about  3  cm. 
long,  the  oropharynx  5  cm.  and  the  laryngopharynx  about  7  cm. 
long.  From  the  incisor  teeth  to  the  esophagus  is  about  5^  to  6>£ 
inches.  Dorsoventrally  the  nasopharynx  is  15  to  18  mm.,  from  the 
septum  of  the  nose  to  the  dorsal  wall;  from  the  glossopalatal  arches 
to  the  dorsal  wall  about  10  mm.;  below  this  the  wall  approach  each 
other.  The  transverse  dimension  at  the  lateral  recesses  is  35  mm.; 
opposite  the  middle  of  the  soft  palate  25  mm.;  opposite  the  inferior 


THE    PHARYNX 


29I 


margin  of  the  laryngeal  opening  45  mm.;  below  this  it  narrows  to 
the  esophagus. 

The  pharynx  is  attached  from  above  downward  to  the  pharyngeal 
spine,  basioccipital,  petrous  portion  of  the  temporal  bone,  auditory 
tube,  internal  pterygoid  plate,  pterygomaxillary  ligament,  mylohyoid 
ridge,  mucous  membrane  of  the  mouth,  base  of  the  tongue,  hyoid 


Fig.  211. —  Median  sagittal  section  through  the  head  and  ncek.  a,  Superior  meatus  of  the 
nose;  b,  middle  meatus  of  the  nose;  c,  inferior  meatus  of  the  nose;  d,  torus  tubarius  (eusta- 
chian cushion);  e,  orifice  of  auditory  tube;/,  palatoglossal  fold;  g.  tonsil;  h.  palatopharyn- 
geal fold;  k,  aryepiglottic  fold;  e,  ventricle  of  the  larynx;  m,  vocal  cord;  n,  vestibule  of  nose. 

bone  and  thyreoid  and  cricoid  cartilages  of  the  larynx  and  below  it 
becomes  continuous  with  the  esophagus. 

The  pharynx  is  divided  into  the  nasopharynx,  oropharynx  and 
laryngopharynx. 

The  nasopharynx  (pars  nasalis)  extends  from  the  base  of  the  skull 
to  the  dorsal  border  of  the  soft  palate.  It  lies  behind  the  nasal 
cavities  and  is  an  accessory  portion  of  the  respiratory  system.  Its 
ventral  wall  is  wanting  and  here  are  seen  the  two  choanal.     Upon 


292  THE    ALIMENTARY    TRACT 

each  lateral  wall  are  several  points  of  interest.  Here  is  seen  the 
pharyngeal  orifice  of  the  auditory  tube  (tuba  auditiva)  bounded  by  a 
hook-shaped  prominence,  the  torus  tubarius,  which  is  open  below. 
The  anterior  limb  of  the  cushion  continues  to  the  soft  palate  and  is 
called  the  salpingo  palatal  fold  [plica  salpingopalatina).  The 
posterior  limb  is  the  longer  and  continues  down  the  pharynx  wall  and 
constitutes  the  salpingopharyngeal  fold  (plica  salpingopharyngea). 
Behind  the  cushion  is  quite  a  deep  recess  called  the  lateral  recess 
of  the  pharynx  (recessus  pharyngeiis).  In  the  middle  of  the  roof  is  a 
small  recess  called  the  pharyngeal  bursa  (bursa  pharyngea).  In  the 
dorsal  wall  are  collections  of  lymphoid  tissue,  the  pharyngeal  tonsils. 
In  infancy  and  childhood  these  masses  frequently  hypertrophy 
constituting  adenoids. 

The  floor  is  formed  by  the  sloping  soft  palate  the  dorsal  border  of 
which  almost  touches  the  dorsal  wall  of  the  pharynx.  The  narrow 
space  intervening  is  called  the  isthmus  of  the  pharynx  (isthmus 
pharyngonasalis). 

The  oropharynx  (pars  oralis)  extends  from  the  lower  border  of 
the  soft  palate  to  the  level  of  the  hyoid  bone.  The  ventral  wall  is 
partly  wanting  representing  the  communication  with  the  oral 
cavity.  The  remainder  of  the  wall  is  made  by  the  base  of  the  tongue. 
Here  are  seen  the  glossoepiglottic  folds  and  the  valleculas.  Upon 
each  lateral  wall  are  seen  two  folds  that  start  at  the  soft  palate  and 
diverge,  the  anterior  passing  to  the  tongue  as  the  glosso palatine 
fold  (arcus  glossopalatinus)  which  contains  the  glossopalatinus 
muscle.  The  posterior  extends  for  some  distance  upon  the  lateral 
pharyngeal  wall  and  is  called  the  pharyngopalatine  fold  (arcus 
pharyngopalatinus)  which  contains  the  pharyngopalatinus  muscle. 
The  wedge-shaped  area  between  these  folds  extending  across  the 
cavity  constitutes  the  isthmus  of  the  fauces  {isthmus  faucium). 
In  this  area  is  seen  the  tonsil  (palatal).  Above  the  tonsil  is  the  sup- 
ratonsillar  fossa  (fossa  supratonsiUaris). 

The  tonsils  (tonsillaz  palatini)  are  situated  between  the  above  folds. 
Each  is  about  1  inch  (2  to  2.5  cm.)  long,  3j  inch  (18mm.)  wide  and 
]j  inch  (12  to  15  mm.)  thick.  Its  pharyngeal  surface  is  covered  by 
mucous  membrane  and  exhibits  a  number  of  pits,  or  crypts  (twelve 
to  fifteen  in  number). 

The  tonsil  is  not  concerned  in  the  process  of  digestion  but  belongs 
to  the  great  group  of  lymphatic  organs.  Its  arteries  are  derived  from 
the  ascending  palatine  and  tonsillar  branches  of  the  external  maxillary 
artery;  the  dorsalis  lingua;  of  the  lingual  and  the  ascending  pharyn- 
geal of  the  external  carotid  artery.  Its  nerves  are  from  the  glosso- 
pharyngeal and  the  pharyngeal  plexus. 

The  laryngopharynx  (pars  laryngea)  extends  from  the  hyoid  bone 
to  the  cricoid  cartilage,  or  to  the  level  of  the  sixth  cervical  vertebra, 


THE    ABDOMEN  293 

behind.  Here  are  seen  the  opening  into  the  larynx,  in  front,  and  the 
opening  into  the  esophagus,  behind.  The  epiglottis  is  seen  here  as 
well  as  the  recessus  pyriformis.  Each  recess  lies  at  the  side  of  the 
laryngeal  aperture  and  is  bounded  laterally  by  the  thyreoid  cartilage 
and  medially  by  the  aryepiglottic  fold. 

The  pharynx  has  seven  communications;  two  nasal,  two  auditory 
tubes,  one  oral,  one  laryngeal  and  one  esophageal. 

The  muscles  of  the  pharynx  are  the  superior,  middle  and  inferior 
constrictors,  the  stylopharyngeus  and  the  pharyngopalatinus. 

The  blood  supply  of  the  pharynx  is  from  the  ascending  pharyngeal, 
the  ascending  palatine  (from  the  external  maxillary)  descending 
palatine  (from  the  internal  maxillary)  dorsalis  lingua?  and  pterygo- 
palatine (from  the  internal  maxillary).  The  nerves  are  from  the 
pharyngeal  plexus  of  the  vaga?,  glossopharyngeal  and  sympathetic 
nerves. 

THE  ESOPHAGUS 

The  esophagus  (Fig.  205)  is  the  narrowest  part  of  the  alimentary 
tract  and  extends  from  the  sixth  cervical  vertebra  to  the  eleventh 
thoracic  vertebra.  It  is  about  10  inches  (25  cm.)  long  and  consists 
of  cervical,  thoracic  and  abdominal  portions.  Its  diameter  varies, 
its  widest  part  being  about  r2'  inch  (12  mm.),  in  the  resting  condition, 
and  then  its  ventral  and  dorsal  walls  are  in  contact.  Distended,  it 
measures  25  to  30  mm.  It  is  not  quite  vertical,  deviating  in  certain 
regions  from  the  midline. 

The  blood  supply  of  the  esophagus  is  derived  from  the  inferior 
thyroid,  descending  thoracic  aorta,  bronchial,  left  gastric  and 
inferior  phrenic  arteries.  The  nerves  are  derived  from  the  vagi 
and  the  sympathetic  system. 

THE  ABDOMEN 

The  abdomen  comprises  the  largest  portion  of  the  trunk.  In  the 
male  it  is  somewhat  barrel-shaped  and  flattened  from  before  backward. 
In  the  female  it  has  the  shape  of  a  flattened,  truncated  cone.  In 
the  midline  the  ventral  wall  is  only  21-;  to  3  inches  from  the  vertebral 
column. 

The  abdomen  represents  the  largest  serous  cavity  of  the  body  and 
consists  of  two  divisions,  the  abdominal  cavity  proper  and  the  pelvic 
cavity.  The  abdominal  cavity  proper  is  bounded  above  by  the  dia- 
phragm and  below  is  continuous  with  pelvic  cavity.  Dorsally  it  is 
bounded  by  the  lumbar  vertebra?  and  iliac  bones,  laterally  by  the 
muscles,  fascia?  and  skin  and  ventrally  by  muscles,  fascia?  and  skin. 
The  upper  part  of  the  abdominal  cavity  is  under  cover  of  the  ribs 
due  to  the  doming  of  the  diaphragm. 


2g4  THE    ALIMENTARY    TRACT 

The  pelvic  cavity  is  bounded  dorsally  by  the  sacrum  and  coccyx, 
laterally  by  the  body  of  the  ischium  and  part  of  the  ilium,  ventrally 
by  the  symphysis  pubis.  It  has  an  inlet  that  gives  communication 
with  the  thoracic  cavity  and  its  boundaries  are  as  follows:  Dorsally 
the  margin  of  the  base  of  the  sacrum,  laterally  the  iliopectineal  lines, 
ventrally  the  crests  of  the  pubic  bones.  It  slants  downward  and 
forward  and  is  heart-shaped.  The  outlet  is  irregular  and  is  bounded 
dorsally  by  the  tip  of  the  coccyx,  laterally  by  the  tuberosities  of  the 
ischia  and  ventrally  by  the  pubic  arches  and  symphysis.  "It  slants 
slightly  downward  and  forward. 
This  is  not  a  true  aperture  but  is 
closed  in  by  the  pelvic  diaphragm 
consisting  mainly  of  the  levatores 
ani  and  the  ischiococcygei  muscles 
and  pelvic  fascia.  This  diaphragm 
is  pierced  by  the  anal  canal,  in  the 
male,  and  the  anal  canal  and  the 
vagina  in  the  female. 

In  the  female  the  pelvis  is  more 
delicate,  wider  and  shallower  than 
in  the  male.  The  inlet  is  larger, 
the  sacrum  shorter  and  less  curved, 
the  outlet  larger  and  the  coccyx 
more  movable,  the  pubic  arch 
larger  and  less  angular. 

The  apertures  of  the  abdominal 
walls  are  the  three  openings  in  the 
diaphragm,  the  openings  in  the 
pelvic  floor  for  the  rectum  the 
urethra  and  in  the  female  the 
vagina;  the  inguinal  canal  for  the 
spermatic  cord  in  the  male,  or  the 
round  ligament  in  the  female,  and 
the  crural  or  femoral  canal  that 
leads  into  the  thigh. 
The  abdomen  is  divided  into 
nine  regions  by  four  lines  or  planes,  two  horizontal  and  two  vertical. 
A  line  drawn  about  the  trunk  at  the  lower  border  of  the  tenth 
costal  cartilage  and  the  superior  part  of  third  lumbar  vertebra  is 
called  the  subcostal  line.  A  second  line  drawn  at  the  level  of  the 
highest  points  of  the  iliac  crests  and  through  the  middle  of  the 
fifth  lumbar  vertebra  is  the  intertubercular  line.  The  two  vertical 
lines  are  drawn  parallel  to  the  long  axis  of  the  body  from  the 
midpoint  of  the  inguinal  ligament  (one  on  each  side).  The  three 
transverse  zones  formed  by  the  horizontal  lines  are  the  costal,  the 


Pig.  212. — Lines  and  regions  of  the  abdo- 
men and  the  viscera  in  each,  i.  Subcostal 
line;  2,  intertubercular  line;  3,  3,  midingui- 
nal  lines;  A,  A,  right  and  left  hypochondriac 
regions;  B.  B,  right  and  left  lumbar  regions; 
C,  C.  right  and  left  inguinal  regions;  D, 
epigastric  region;  E,  umbilical  region;  F, 
hypogastric  region. 


THE  CONTENTS  OF  THE  ABDOMEN 


295 


umbilical  and  the  hypogastric.  The  two  vertical  lines  divide  these 
zones  into  nine  regions.  In  the  costal  zone  the  regions  are  right 
hypochondriac,  epigastric  and  left  hypochondriac.  In  the  umbilical 
zone  they  are  right  lumbar,  umbilical  and  left  lumbar  regions.  In  the 
hypogastric  zone  lie  the  right  iliac,  hypogastric  and  left  iliac  regions. 

A  horizontal  line  drawn  about  the  trunk  at  a  point  midway 
between  the  superior  border  of  the  crest  of  the  pubis  and  the  inferior 
margin  of  the  sternum  and  at  the  level  of  the  first  lumbar  vertebra, 
behind,  is  the  transpyloric  line. 

The  contents  of  the  abdomen  are  the  stomach,  intestines,  liver, 
pancreas,  spleen,  kidneys,  ureters,  bladder,  adrenals,  seminal  vesicles, 
prostate  and  vasa  deferentia  (in  the  male)  and  the  ovaries,  oviducts, 


213. — Outline  of  some  of  the  organsof  the  thorax  Fig.  214. — Outline    of     some     of    the 

and  abdomen,  on  the  ventral  body  wall.      (From  a  photo-         organs  of  the    thorax  and  abdomen,    on 
graph. 1  the  dorsal     body    wall.      (From    a    photo- 

graph.) 

uterus  and  vagina  (in  the  female)  nerves,  sympathetic  ganglia,  blood- 
vessels, lymph  channels  and  lymph  nodes.  These  are  located  in  the 
various  regions  as  follows: 

Right  Hypochondrium. — Right  lobe  of  the  liver,  gall-bladder, 
duodenum,  hepatic  flexure  of  the  colon  and  the  upper  part  of  the 
right  kidney. 

Epigastrium. — Part  of  right  and  left  lobes  of  the  liver,  the  pylorus 
and  bulk  of  the  stomach,  aorta,  celiac  axis,  celiac  ganglia  and 
pancreas. 

Left  Hypochondrium. — Spleen,  tail  of  the  pancreas,  splenic  flexure 
of  the  colon,  upper  part  of  left  kidney  and  the  left  portion  of  the 
greater  curvature  of  the  stomach. 


296  THE    ALIMENTARY    TRACT 

Rig/it  Lumbar  Region. — Liver,  part  of  the  right  kidney,  coils  of 
the  small  intestine  and  ascending  colon. 

Umbilical  Region. — The  transverse  colon,  the  greater  curvature  of 
the  stomach,  coils  of  the  small  intestine,  the  mesentery  and  great 
omentum. 

Left  Lumbar  Region. — Lower  part  of  the  left  kidney,  descending 
colon  and  coils  of  the  small  intestine. 

Right  Iliac  Region. — Cecum,  appendix,  ileocecal  junction  and 
right  ureter. 

Hypogastric  Region. — Coils  of  the  small  intestine,  fundus  of  bladder 
(when  distended)  uterus  (during  pregnancy). 

Left  Iliac  Region. — Descending  colon  and  left  ureter. 

THE  PERITONEUM 

The  peritoneum  is  a  serous  membrane  that  lines  the  abdominal 
cavity  and  more  or  less  completely  invests  the  various  organs.  In 
the  male  this  is  a  closed  sac,  but  in  the  female  the  oviducts  open  into 
the  peritoneal  cavity.  The  tunica  vaginalis  of  the  testes  and  the 
serous  lining  of  the  scrotal  compartments  are  derived  from  the  peri- 
toneum. That  portion  lining  the  walls  of  the  peritoneal  cavity  is 
the  peritoneum  parietale  and  that  upon  the  organs  is  the  peritoneum 
viscerale. 

Peritoneal  folds  are  of  three  kinds: 

1.  Omenta,  those  folds  that  connect  the  stomach  to  other  organs. 
These  are  the  gastrocolic,  or  great  omentum  {omentum  majus),  which 
extends  from  the  greater  curvature  of  the  stomach  to  the  transverse 
colon.  The  gaslrohepalic,  or  lesser  omentum  (omentum  minus), 
extends  from  the  lesser  curvature  of  the  stomach  to  the  transverse 
fissure  of  the  liver.  The  gastrosplenic  omentum  extends  from  the 
greater  curvature  of  the  stomach  to  the  spleen. 

2.  Mesenteries  that  connect  parts  of  the  intestine  to  the  dorsal 
body  wall.  These  are  the  mesentery  proper  ( mesenterium)  compris- 
ing the  mesojejunum  and  mesoileum,  the  transverse  mesocolon 
(mesocolon  transversum)  mesosigmoid  (mesocolon  pehinum)  and 
mesoappendix. 

3.  Ligaments,  folds  of  peritoneum  that  connect  organs  other 
than  the  gastrointestinal  tract  to  the  body  wall.  These  are  the 
falciform,  the  right  and  left  lateral  ligaments  of  the  liver,  broad 
ligament  of  the  uterus,  false  ligaments  of  the  bladder,  etc. 

Owing  to  the  peculiarity  in  development  of  the  greater  and  lesser 
omenta  of  the  stomach  a  portion  of  the  general  peritoneal  cavity, 
the  lesser  sac  (bursa  omentalis)  is  cut  off  from  the  remainder  which 
then  constitutes  the  greater  sac.  These  two  sacs  communicate 
with  each  other  underneath  the  liver  through  the  foramen  of  Winslow 
(foramen  epiploicum). 


THE    PERITONEUM 


297 


The  lesser  sac  is  bounded  by  two  layers  of  peritoneum,  ventral 
and  dorsal.  The  ventral  layer  invests  the  caudate  lobe  of  the  liver 
and  continues  to  the  dorsal  edge  of  the  portal  fissure  and  from  here, 
and  from  the  fissure  for  the  ligamentum  venosum  it  passes  to 
the  lesser  curvature  of  the  stomach  as  the  dorsal  layer  of  the  gas- 
trohepatic  omentum.  It  invests  about  the  entire  dorsoinferior 
surface  of  the  stomach,  being  continued  as  the  dorsal  layer  of  the 
great  omentum  to  the  lower  border  of 
this  fold  where  it  becomes  continuous 
with  the  dorsal  layer  of  the  lesser  sac. 
From  the  upper  part  of  the  greater 
curvature  of  the  stomach  it  continues 
to  the  spleen  as  the  dorsal  layer  of  the 
gastrosplenic  omentum. 

The  dorsal  layer  of  the  lesser  sac  passes 
from  the  foramen  of  Winslow  over  the 
inferior  vena  cava  and  the  celiac  axis, 
covers  a  small  area  of  the  diaphragm 
behind  the  caudate  lobe,  thence  passing 
to  the  left,  it  covers  the  upper  surface 
of  the  pancreas,  the  left  adrenal  and 
superior  pole  of  the  left  kidney  and  part 
of  the  gastric  area  of  the  spleen.  From 
the  pancreas  it  continues  as  the  ventral 
layer  of  the  transverse  mesocolon,  over 
the  colon  and  from  this  region  it  con- 
tinues as  the  ventral  layer  of  the  dorsal 
fold  of  the  great  omentum  to  its  lower 
border,  where  it  becomes  continuous 
with  the  dorsal  layer  of  the  ventral  fold 
previously  described. 

The  greater  sac  constitutes  the  bulk 
of  the  peritoneal  cavity.  The  ventral 
layer  starts  at  the  uncovered  area  of  the 
liver  (upper  margin)  and  continues  on 
to  the  under  surface  of  the  diaphragm 
down  the  ventral  body  wall  to  the  pelvis. 
a  fold  attached  to  the  ventral  body  wall  and  the  under  surface  of  the 
diaphragm  is  reflected  upon  the  ventral  and  superior  surface  of  the 
liver  as  the  falciform  ligament  of  the  liver.  In  the  free  edge  of  this 
fold  is  the  round  ligament  of  the  liver. 

The  dorsal  layer  starts  at  the  upper  margin  of  the  uncovered 
area  of  the  liver,  forming  here  the  upper  leaflet  of  the  coronary 
ligament;  it  invests  the  superior,  right  and  ventral  surfaces  of  the 
right  and  left  lobes  and  passes  to  the  inferior  surface  at  the  ventral 


Fig.  215. —  Medial  sagittal  section 
of  female  showing  the  reflections  of 
the  peritoneum  (digrammatic).  .4, 
Foramen  epiploicum;  B,  bladder;  C, 
transverse  colon;  D.  duodenum;  E. 
rectum;  Mt's,  mesentery;  P,  pan- 
creas; SI,  small  intestine;  V ,  uterus. 

From  the  umbilical  region 


298 


THE    ALIMENTARY    TRACT 


margin  of  the  liver.  Here  it  passes  backward  and  upward  over  the 
right  and  left  lobes  to  the  portal  fissure  while  lateral  to  this  fissure 
the  peritoneum  spreads  upon  the  remainder  of  the  inferior  surface 
(except  the  caudate  lobe  and  the  inferior  vena  cava)  to  the  lower 
margin  of  the  uncovered  area  forming  here  the  lower  leaflet  of  the 
coronary  ligament;  upon  the  left  it  continues  to  the  diaphragm  as 
part  of  the  left  lateral  ligament  and  upon  the  right  side  as  part  of 
the  right  lateral  ligament.  The  portion  extending  to  the  left  covers 
the  dorsal  abdominal  wall  lying  ventral  to  the  outer  and  upper  part 
of  the  left  kidney  and  extending  from  here  to  the  spleen  as  the  li- 
enorenal  ligament.  This  layer  then  passes  around  and  invests  the 
spleen  covering  the  renal,  colic  and  part  of  the  gastric  areas  con- 
tinues to  the  greater  curvature  of  the  stomach  as  the  ventral  layer 


FiG.  216. — Transverse  section  of  the  abdomen,  at  the  level  of  the  foramen  epiploicum, 
showing  the  reflections  of  the  peritoneum  (diagrammatic).  A,  Aorta;  B,  inferior  vena  cava; 
C.  gastrohepatic  omentum;  K,  K.  kidneys. 

of  the  gastrosplenic  omentum.  Upon  the  right  side  the  peritoneum 
passes  upon  the  diaphragm  as  far  to  the  left  as  the  esophagus,  form- 
ing here  the  fold  called  the  gastrophrenic  ligament.  It  also  con- 
tinues downward  over  the  right  adrenal  and  kidney,  to  the  duodenum 
and  hepatic  flexure  of  the  colon,  both  of  which  it  partially  invests. 
From  the  portal  fissure  the  dorsal  layer  of  the  greater  sac  continues 
down  to  the  lesser  curvature  of  the  stomach  as  the  ventral  layer  of 
the  gastrohepatic  omentum;  from  the. lesser  curvature  it  invests 
the  superior  surface  of  the  stomach  and  the  greater  curvature, 
from  which  it  is  continuous  with  the  ventral  layer  of  the  ventral  fold 
of  the  great  omentum  to  the  lower  border  of  that  fold.  From  the 
lower  border  of  the  great  omentum  it  continues  upward  to  the 
transverse  colon  as  the  dorsal  layer  of  the  dorsal  fold  of  the  great 
omentum  and  from  the  colon  up  to  the  dorsal  body  wall  it  forms  the 


THE    PERITONEUM 


299 


dorsal  layer  of  the  transverse  mesocolon  to  the  pancreas.  At  the 
pancreas  the  peritoneum  passes  downward  over  the  third  part  of 
the  duodenum  to  the  oblique  mesentery  of  the  small  intestines. 
Here  it  forms  the  right  layer  of  the  mesentery,  invests  the  bowel  and 
then  passes  to  the  dorsal  body  wall  as  the  left  layer  of  the  mesentery; 
it  then  continues  down  along  the  dorsal  body  wall  to  the  left  and 
right,  investing  the  sides  and  ventral  walls  of  the  ascending  and 
descending  colons  (with  cecum  and  appendix).  In  the  left  iliac 
fossa  it  completely  invests  the  sigmoid  colon  forming  for  it  a  mesen- 
tery that  shortens  as  the  pelvic  cavity  is  reached  and  ending  at  the 
beginning  of  the  rectum.  In  the  pelvic  cavity  the  dorsal  layer 
descends  upon  the  front  and  sides  of  the  rectum  lessening  at  the 
sides  so  that  at  about  the  middle  of  this  organ  the  entire  peritoneum 
leaves  the  rectum  to  be  carried  forward,  in  the  male,  to  the  back  of 


■  section  of  the  abdomen  at  a  more  caudal  level  (diagrammatic), 
nferior  vena  cava;  C,  ascending  colon;  C  descending  colon. 


the  bladder  and  sides  of  the  pelvis,  forming  the  rectovesical  pouch. 
It  then  continues  over  the  superior  part  and  lateral  surfaces  of  the 
bladder  to  the  ventral  abdominal  wall,  becoming  here  continuous 
with  the  ventral  layer. 

In  the  female  the  peritoneum  is  reflected  from  the  rectum  to  the 
upper  part  of  the  dorsal  wall  of  the  vagina  and  then  to  the  dorsal 
wall  of  the  uterus  and  broad  ligament,  over  the  fundus  and  the  ovi- 
ducts to  the  ventral  surface  of  fundus  and  body  of  the  uterus  and 
the  broad  ligament;  it  then  continues  to  the  back  of  the  bladder,  up 
over  the  superior  part  of  the  lateral  surfaces  of  this  organ  to  the 
ventral  body  wall.  In  the  female  the  fossa  between  the  rectum, 
behind,  and  uterus  and  vagina,  in  front,  is  the  pouch  of  Douglas 
(rectouterine)  and  between  the  uterus,  behind,  and  the  bladder, 
in  front,  the  space  is  called  the  uterovesical  pouch. 


300  THE    ALIMENTARY    TRACT 

At  the  sides  of  the  body  wall  the  ventral  and  dorsal  layers  of  the 
greater  sac  are  continuous  with  each  other. 

The  organs  completely  invested  by  the  peritoneum  are  as  foliows: 
Spleen,  jejunum,  ileum,  cecum,  appendix,  transverse  colon,  sigmoid 
colon  and  the  oviducts  (in  the  female). 

Those  partially  invested  are:  Liver,  stomach,  duodenum,  ascending 
and  descending  colons,  rectum  (upper  part),  bladder,  uterus  and 
vagina  (in  the  female). 

Those  uninvested  are:  Kidneys,  adrenals,  ureters,  rectum  (lower 
part),  anal  canal,  pancreas,  seminal  vesicles,  vas  and  prostate  (in  the 
male),  and  the  urethra. 

THE  STOMACH  (VENTRICULUS) 

The  stomach  (ventriculus)  lies  in  the  epigastric,  umbilical  and  left 
hypochondriac  regions.  The  direction  of  its  long  axis  varies 
from  oblique  to  nearly  horizontal,  depending  upon  the  quantity  of 
its  contents.  The  space  occupied  is  called  the  stomach-chamber. 
When  viewed  from  the  side  this  space  is  somewhat  triangular  with 
curved  sides.  The  floor  slants  downward  (caudad)  and  ventrally; 
it  is  formed  by  the  upper  surface  of  the  pancreas,  the  transverse 
mesocolon,  transverse  colon,  spleen,  right  adrenal,  and  the  upper 
pole  of  the  left  kidney.  The  roof  is  formed  by  the  inferior  surface 
of  the  left  lobe  of  the  liver  and  the  diaphragm.  The  ventral  wall 
is  formed  by  the  ventral  abdominal  wall  and  the  diaphragm. 

When  empty  and  contracted  the  stomach  is  sausage-shaped  and 
almost  vertical.  As  the  stomach  fills  it  dilates  at  the  fundus  first 
and  at  the  pyloric  portion  last. 

The  stomach  presents  two  orifices,  cardia  and  pylorus,  two  surfaces, 
ventral  and  dorsal,  and  two  borders,  the  greater  and  lesser  curvatures. 
It  is  divided  into  fundus,  body  and  pyloric  portion. 

The  cardiac  orifice  (cardia)  is  situated  about  2  inches  (5  cm.) 
to  the  left  of  the  midline  at  the  level  of  the  eleventh  thoracic  vertebra, 
behind,  or  1  inch  to  the  left  of  the  seventh  sternochondral  junction, 
in  front.     It  is  fixed  in  position. 

The  pyloric  orifice  (pylorus)  is  situated  about  12  to  1  inch  (i1., 
to  2.5  cm.)  to  the  right  of  the  midline  at  the  level  of  the  first  lumbar 
vertebra.  In  the  distended  stomach  the  pylorus  moves  an  inch  or 
so  to  the  right.     It  opens  into  the  duodenum. 

The  ventral  surface  (paries  anterior)  is  convex  and  is  in  contact 
with  the  roof  and  ventral  wall  of  the  stomach  chamber  when  the 
organ  is  distended.  When  empty,  the  transverse  colon  lies  ventral 
to  it.     It  is  more  extensive  than  the  dorsal  surface. 

The  dorsal  surface  (paries  posterior)  is  more  flattened  and  less 
extensive  than  the  preceding  and  is  in  contact  with  the  floor  of  the 


THE    STOMACH 


30I 


stomach  chamber.  This  surface  may  be  divided  by  a  slight  ridge 
into  an  upper  and  a  lower  area. 

The  greater  curvature  (curvatura  venlriculus  major)  is  convex  and 
starts  to  the  left  of  the  esophagus  in  the  incisura  cardiaca  and  extends 
to  the  pylorus.  This  margin  is  12  to  16  inches  long  in  the  distended 
stomach  (three  to  four  times  that  of  the  lesser  curvature)  and  has 
the  great  omentum  attached  along  the  greater  part  of  its  extent. 

The  lesser  curvature  (curvatura  ventriculus  minor)  is  somewhat 
concave,  extends  from  the  cardiac  region  to  the  pylorus;  it  is  only 
3  to  4  inches  in  length  and  has  the  gastrohepatic  omentum  attached 
to  it.     Near  the  pylorus  is  the  incisura.  annularis. 

The  fundus  (fundus  ventriculi)  is  the  dilatation  to  the  left  of  the 
esophagus  and  it  extends  1  to  2  inches  (2.5  to  5  cm.)  above  the  level 
of  the  cardiac  orifice.  It  constitutes  a  little  less  than  one-third  of 
the  stomach.     The  body  (corpus  ventriadi)  is  the  next  portion  and 


ltU3u.|o,r 


-The  parts  of  the  stomach  shown 
in  the  distended  organ. 


Fig.  219. — Form  and  position  of  the 
empty  contracted  stomach. 

connects  the  fundus  and  pyloric  portions.  It  constitutes  a  little 
over  one-third  of  the  stomach.  The  pyloric  end  (pars  pylori, a\ 
constitutes  about  one-third  and  is  separated  from  the  body  by  the 
incisura  annularis.  It  is  sometimes  separated  into  a  dilated  first 
part,  the  pyloric  vestibule  (antrum  pyloricum)  and  a  second  tubular 
portion,  the  pyloric  canal. 

The  measurements  of  the  distended  stomach  are,  length  10  to  12 
inches  (25  to  30  cm.),  lateral  4  to  5  inches  (10  to  12.5  cm.),  and  dorso- 
ventral  3  to  4  inches  (7.5  to  10  cm.).  Its  capacity  is  usually  1  quart 
(40  ounces)  though  some  give  4  to  5  pints  as  the  capacity.  Its 
weight  is  41.,  ounces  (135  grams). 

The  stomach  is  almost  completely  invested  with  peritoneum,  the 
uncovered  area  being  just  behind  and  to  the  left  of  the  cardia.  It  is 
triangular  in  shape,  measures  about  2  inches  along  the  base  and  \V^ 
inches  high.     The  stomach  is  connected  to  the  liver  by  the  gastro- 


302  THE    ALIMENTARY    TRACT 

hepatic  omentum;  to  the  colon  by  the  gastrocolic  omentum  and  to 
the  diaphragm  by  a  small  fold,  the  gastrophrenic  ligament. 

The  interior  of  the  stomach  exhibits  many  folds  chiefly  longi- 
tudinal in  direction,  consisting  of  mucous  and  submucous  coats. 
These  folds  are  the  ruga;.  Minute  orifices  representing  the  gastric 
pits,  or  crypts,  are  seen  throughout  the  entire  surface.  At  the  pyloric 
orifice  a  distinct  fold  is  seen,  constituting  the  pyloric  valve.  Within 
this  fold  is  a  strong  ring  of  circularly  disposed  smooth  muscle  tissue, 
the  sphincter  pylori  muscle. 

The  stomach  is  supplied  by  the  following  arteries  (branches  of 
the  celiac  axis):  The  gastric  (from  celiac  axis  direct),  pyloric  (from 
the  hepatic),  right  gastroepiploic  (gastroduodenale),  left  gastro- 
epiploic (splenic),  vasa  brevia  (splenic).  The  veins  empty  into  the 
superior  mesenteric  and  splenic  veins. 

The  nerves  are  derived  from  the  vagals  and  the  solar  plexus 
(ganglion  celiaca)  of  the  sympathetic;  branches  from  these  form  the 
plexuses  of  Auerbach  (plexus  myentcricus)  and  Meissner  (plexus 
submucosce)  in  the  walls  of  the  organ. 

SMALL  INTESTINE  (INTESTINI  TENTJE) 

The  small  intestine  consists  of  duodenum,  jejunum  and  ileum  and 
is,  after  death,  20  to  22  feet  in  length  (22.5  feet  in  the  male  and  23 
feet  in  the  female).  The  diameter  varies  from  2  inches  (5  cm.)  at 
the  duodenum,  to  a  little  over  1  inch  (27  mm.)  at  the  ileum. 

The  duodenum  is  n  inches  (27.5  cm.)  in  length  and  starts  at  the 
right  side  of  the  first  lumbar  vertebra  and  ends  at  the  left  of  the 
second  lumbar  vertebra  having  a  C-,  U-  or  V-shape.  Its  two  ex- 
tremities are  only  about  2  inches  (5  cm.)  apart.  It  is  the  largest  part 
of  the  small  intestine.  It  consists  of  superior  (pars  superior), 
descending  (pars  descendens) ,  transverse  (pars  horizontal  is)  and  ascend- 
ing (pars  ascendens)  portions.  In  the  cavity  of  the  duodenal  loop 
is  placed  the  head  of  the  pancreas.  All  parts  do  not  lie  in  the  same 
plane.  The  first  part  is  slightly  movable  being  almost  invested  by 
peritoneum  while  the  remainder  is  fixed  being  only  partially  invested. 
In  this  it  is  readily  distinguished  from  the  remainder  of  the  intestine. 
At  its  termination  as  it  turns  ventrally  to  continue  as  jejunum 
(duodenojejunal  junction)  it  is  bound  to  the  body  wall  by  a  fold,  the 
suspensory  ligament  of  Treitz,  containing  some  smooth  muscle  tissue, 
the  suspensory  muscle  (m.  suspensorius  duodeni).  As  a  whole  the 
duodenum  is  incompletely  invested  with  peritoneum. 

The  interior  of  the  duodenum  varies  in  appearance.  The  first 
part  is  smooth  but  this  condition  is  soon  changed  by  the  appearance 
of  circular  folds,  the  plica;  eircidares,  or  valvules  conniventes.  In 
the  descending  portion  is  a  longitudinal  fold  representing  the  course 


THE    DUODENUM 


3°3 


of  the  bile  and  pancreatic  ducts.     At  the  lower  end  of  this  fold  is 
a  papilla  (papilla  duodeni)  at  which  the  above  ducts  empty  into  the 

4 


Fig.   220. — A  diagram  of  the  alimentary  tract. 

duodenum.     This  papilla  is  usually  3J-2  to  4  inches  from  the  pyloric 
orifice. 


3°4 


THE    ALIMENTARY    TRACT 


The  jejunum  (intestinum  jejunum)  represents  about  two-fifths 
(8  feet)  of  the  small  intestine.  It  has  a  greater  diameter,  ij^  to 
ili  inches  (3.75  to  3  cm.)  than  the  ileum,  its  walls  are  thicker  and 


Bi\1wTWlrlV    Hc.-t.cfl 


Fig.  221. — Ventral  view  of  the  duodenum,  pancreas  and  the  neighboring  organs. 

redder,  the  plica;  circulares  are  larger  and  more  numerous  than 
in  the  ileum  and  the  villi  are  more  numerous  and  broader. 


-Interior  of  the  jejunum  showing  the  plica?  circula 


iFrotn  a  photograph.) 


The  ileum  (intestinum  ileum)  constitutes  about  three-fifths  (12 
feet)  of  the  small  intestine.  It  is  about  1  inch  (2.5  cm.)  in  diameter, 
its  walls  are  thin  and  pale,  the  plicae  circulares  are  few  and  small  and 
the  villi  few  and  slender.     Both  of  these  portions  of  the  small  in- 


THE    CECUM  305 

testine  are  completely  invested  with  peritoneum  and  are  suspended 
from  the  dorsal  body  wall  by  the  mesentery.  The  coils  of  the 
jejunum  lie  chiefly  in  the  upper  and  left  part  of  the  abdominal  cavity, 
the  first  third  of  the  ileum  in  the  left  iliac  fossa,  and  the  remainder 
in  the  lower  right  portion  of  the  abdominal  cavity  and  even  in  the 
pelvic  cavity. 

The  small  intestine  receives  its  blood  supply  from  the  following 
vessels:  Duodenum  from  the  pyloric  and  superior  pancreatico- 
duodenale  (branches  of  the  hepatic  artery)  and  inferior  pancreatico- 
duodenale  (from  the  superior  mesenteric  artery).  The  veins  return 
the  blood  to  the  superior  mesenteric  and  portal  veins. 

The  jejunum  and  bulk  of  the  ileum  receive  their  blood  from  the  vasa 
intestini  tenuis  (from  the  superior  mesenteric  artery)  and  the  re- 
mainder of  the  ileum  from  the  ileal  vessels  (ileocolic  branch  of  the 
superior  mesenteric  artery).  The  veins  return  the  blood  to  the 
superior  mesenteric  vein. 

The  nerves  are  derived  from  the  celiac  plexus  of  the  sympathetic- 
system.  Branches  from  this  plexus  form  the  plexuses  of  Auerbach 
(plexus  myentericus)  and  Meissncr  (pi.  submucosa)  in  the  walls  of  the 
intestine.     Some  branches  of  the  right  vagus  join  the  latter  plexuses. 

THE  LARGE  INTESTINE  (INTESTINTJM  CRASSUM) 

The  large  intestine  consists  of  cecum,  colon,  rectum,  anal  canal 
and  anus  (Fig.  220). 

The  large  bowel  presents  a  sacculated  appearance.  This  condi- 
tion is  due  to  the  three  longitudinal  bands,  or  tenia  coli.  These 
bands  represent  the  longitudinal  muscle  tissue  of  the  large  intestine 
and  as  these  bands  are  about  one-sixth  shorter  than  the  intestine 
they  cause  the  sacculations.  They  arise  at  the  base  of  the  appendix 
and  are  nearly  equidistant  from  one  another.  They  extend  to  the 
rectum  where  they  end  by  spreading  out  to  form  a  complete  longi- 
tudinal layer.  If  the  tenia?  be  removed  the  sacculations  disappear 
and  the  bowel  is  of  a  cylindrical  form.  All  along  the  large  intestine 
are  seen  little  tabs  of  fat  surrounded  by  peritoneum  called  the 
appendices  epiploic^. 

The  cecum  (intestinum  cecum)  is  the  blind  portion  of  the  large 
intestine.  It  is  about  2.5  inches  (6.5  cm.)  long  and  3  inches  (7.5 
cm.)  wide.  It  lies  in  the  right  iliac  fossa  and  extends  as  high  as 
the  intertubercular  plane.  The  interior  of  the  cecum  shows  some 
folds  of  the  mucosa  and  submucosa.  The  superior  end  is  continuous 
with  the  colon.  The  opening  of  the  ileum  is  guarded  by  the  ileo- 
cecal valve  (valvula  coli)  that  consists  of  two  segments,  upper  (labium 
supcrius)  and  lower  (labium  inferius).  About  1  li  inches  below  the 
ileocecal  orifice  is  the  appendiculer  orifice  and  this  may  be  guarded 
by  a  valve. 


306 


THE    ALIMENTARY    TRACT 


The  cecum  is  usually  entirely  invested  with  peritoneum  but  it  has 
no  mesentery. 

The  appendix  (processus  vermiformis)  is  the  smallest  part  of  the 
intestine.  It  has  been  known  to  be  absent  and  in  other  cases  as 
long  as  9  inches  ("22. 5  cm.).  Its  average  is  about  3  inches  (7.5  cm.) 
in  length  and  }-i  inch  (6  mm.)  in  diameter.  Its  orifice,  guarded  by  a 
valve  (valvula  processus  vermiformis)  usually  is  considered  half  way 
on  a  line  between  the  anterior  superior  spine  of  the  ilium  and  the 
umbilicus;  this  is  called  McBurney's  point.  The  appendix  is  com- 
pletely surrounded  by  peritoneum  and  possesses  a  mesentery,  the 
mesoappendix. 

The  colon  (Figs.  213  and  220)  consists  of  four  parts,  ascending, 
transverse,  descending  and  sigmoid  flexure. 

The  ascending  colon  (colon  ascendens) 
is  5  to  8  inches  (.12.5  to  20  cm.)  long 
and  extends  from  the  intertubercular 
plane  to  the  under  surface  of  the  liver, 
where  it  turns  ventrally  and  to  the  left 
Jg  SL  as  the  hepatic  flexure.     It  is  wider  and 

K^s^^^gS^^^  more   prominent    than    the   descending 

colon;  it  is  usually  invested  upon  its 
ventral  and  two  lateral  surfaces  with 
peritoneum  and  is,  therefore,  fixed  in 
position.  It  lies  in  the  right  lumbar  and 
partly  in  the  right  hypochondriac 
regions. 

Fig.  223.— Cecum  with  part  of  At  the  liver  the  colon  bends  sharply 
the    ventral    wall    removed,    a,   to  the  left  and  ventrallv  and  this  part 

Ileocecal     valve     and     orifice;     B,     .  ..      .    .         .    ,     .,  •  \  n  /n 

appendicular  orifice.  is  called  theriglit  (hepatic)  flexure  (nexura 

coli  dextra)  and  produces  the  colic  im- 
pressions upon  the  visceral  surface  of  the  liver. 

The  transverse  colon  (colon  transversum)  is  from  15  to  20  inches 
(37-5  to  50  cm.)  long;  it  begins  at  the  hepatic  flexure  and  extends 
across  the  body  in  an  arched  manner  (convexity  downward)  to  the 
spleen  where  it  ends  at  the  splenic  flexure.  The  first  and  last  por- 
tions are  fixed  in  position,  but  the  intervening  portion  is  freely 
movable  possessing  a  long  mesentery,  the  transverse  mesocolon. 
Its  extremities  lie  in  the  right  and  left  hypochondriac  regions  while 
the  middle  portion  lies  in  the  umbilical  and  even  in  the  hypogastric 
region. 

At  the  spleen  the  transverse  colon  turns  sharply  downward 
(caudad),  forming  the  left  (splenic)  flexure  (flexura  coli  sinistra). 
This  lies  at  a  higher  level  than  the  right  flexure. 

The  descending  colon  (colon  descendens)  is  about  4  to  6  inches 
(10  to  15  cm.)  long  and  starts  at  the  splenic  flexure  and  extends  to 


THE    ANAL    CANAL  307 

the  left  iliac  crest.  It  is  about  i}2  inches  (3.75  cm.)  in  diameter  and 
is  partly  invested  with  peritoneum;  it  is  fixed  in  position.  It  lies 
in  the  left  hypochondriac  and  lumbar  regions  and  bends  slightly 
toward  the  midline  at  the  level  of  the  left  kidney. 

The  sigmoid  flexure,  17  to  20  inches  (42.5  to  50  cm.)  in  length, 
consists  of  two  parts,  the  iliac  and  pelvic  colons.  The  iliac  colon, 
about  5  to  6  inches  (12.5  to  15  cm.)  long,  extends  from  the  crest  of 
the  ilium  to  the  brim  of  the  pelvis.  It  is  completely  invested  with 
peritoneum  but  has  no  mesentery.  It  lies  in  the  left  iliac  and  the 
hypogastric  regions.  The  pelvic  colon,  about  12  to  17  inches  (30 
to  42.5  cm.)  in  length,  extends  from  the  brim  of  the  pelvis  to  the 
third  sacral  segment  in  an  irregular  loop.  This  constitutes  a  large 
coil  that  is  completely  invested  with  peritoneum  and  has  a  well- 
developed  mesentery  that  shortens  as  the  end  of  this  portion  of  the 
bowel  is  reached.  This  mesentery  is  referred  to  as  the  mesosigmoid 
for  both  parts  as  a  whole,  or  pelvic  mesocolon. 

The  rectum  (iutestinum  rectum)  about  5  to  6  inches  (12.5  to  15 
mm.),  extends  from  the  third  segment  of  the  sacrum  to  a  point 
about  1*2  inches  (3.75  cm.)  in  front  of  the  tip  of  the  coccyx.  The 
first  part  is  only  partially  invested  by  peritoneum  and  the  last  por- 
tion not  at  all.  Its  diameter  varies,  being  smallest  at  the  beginning 
and  largest  nearest  the  anal  canal.  This  dilated  portion  is  called 
the  ampulla  (ampulla  recti).  When  empty  the  diameter  is  about 
1  inch  (2.5  cm.)  but  when  distended  it  may  be  3  inches  (7.5  cm.). 

The  rectum  is  not  straight,  as  its  name  indicates,  but  shows  a 
curve  from  before  backward  as  it  follows  the  curve  of  the  sacrum. 
Viewed  from  the  front  it  shows  usually  three  curves;  the  upper  and 
the  lower  have  the  concavity  to  the  left  and  the  middle  curve  to 
the  right.  These  are  not  sacculations  but  are  due  to  the  projection 
of  the  coats  into  the  lumen  of  the  organ  forming,  thus,  three  well- 
marked  shelves,  the  rectal  valves  (plicce  transvcrsales  recti).  These 
valves  extend  from  a  half  to  two-thirds  of  the  way  across  the  lumen 
and  serve  to  support  the  weight  of  the  fecal  matter. 

The  anal  canal  (pars  Orudis  recti)  is  the  slit-like  continuation  of 
the  bowel.  It  is  from  1  to  i'2  inches  (2.5  to  3.75  cm.)  in  length 
and  '_>  to  34  inch  (12  to  18  mm.)  dorsoventrally.  It  lies  between 
the  levatores  ani  muscles  and  extends  backward  and  downward  at 
an  angle  of  about  45°  to  the  horizontal  plane,  from  the  end  of  the 
rectum  to  the  anal  orifice.  The  circularly  disposed  smooth  muscle 
fibers  extend  from  the  beginning  to  about  }i  inch  from  its  end  and 
constitute  the  internal  sphincter  muscle.  Around  the  lower  two- 
thirds  is  a  strong  band  of  circularly  arranged  voluntary  striated 
muscle  called  the  external  sph  'ncter. 

The  interior  of  the  anal  canal  shows,  in  its  upper  and  middle 
thirds,  a  number  (five  to  ten)  of  vertical  folds  called  the  columns  of 


308  THE    ALIMENTARY    TRACT 

Morgagni  {eolumnce  rectales).  Between  these  are  little  depressions 
{sinuses  rectales)  bounded  below  by  crescentic  folds  called  the  anal 
valves. 

The  anal  orifice  is  the  lower  aperture  of  the  alimentary  tract. 
This  orifice  is  irregular  and  is  usually  surrounded  by  hairs,  sebaceous 
and  modified  sweat  glands  (glandule?  circumanales).  At  the  orifice 
the  mucous  membrane  of  the  rectum  passes  into  the  skin  without 
any  sharp  line  of  demarcation. 

The  blood-vessels  that  supply  the  large  bowel  are  as  follows: 
Cecum  and  appendix  by  the  ileocecal  artery  (from  the  ileocolic  branch 
of  the  superior  mesenteric  artery) ;  the  ascending  colon  by  the  right 
colic  (from  the  superior  mesenteric) ;  the  transverse  colon  by  the  mid- 
dle colic  (from  the  superior  mesenteric)  and  the  left  colic  (from  the 
inferior  mesenteric) ;  sigmoid  colon  by  the  sigmoid  branches  of  the 


Fig.   224. — Lower  part  of  the  rectum  and  the  anal  canal.      C,  C,  columns  of    Morgagni;  Vj 
anal  valves. 

inferior  mesenteric  artery;  the  rectum  by  the  superior  hemorrhoidal 
(from  the  superior  mesenteric),  the  middle  hemorrhoidal  (from  the 
internal  iliac)  and  the  inferior  hemorrhoidal  (from  the  internal 
pudic). 

The  venous  blood  of  the  rectum  passes  in  two  directions.  There 
are  two  venous  plexuses  in  the  rectum,  internal  and  external.  The 
internal  hemorrhoidal  plexus  gives  rise  to  the  inferior  hemorrhoidal 
veins  that  empty  into  the  internal  pudic  vein  which  is  a  tributary 
to  the  inferior  vena  cava  through  the  internal  and  common  iliac 
veins.  The  external  hemorrhoidal  plexus  gives  rise  to  the  superior 
hemorrhoidal  vein  that  empties  into  the  inferior  mesenteric  vein 
which  is  a  tributary  to  the  portal  vein.  The  blood  that  is  distrib- 
uted by  the  inferior  mesenteric  artery  is  returned  by  venous  channels 
that  correspond  to  the  arterial  branches;  these  ultimately  form  the 
inferior  mesenteric  vein  that  empties  into  the  splenic  vein,  a  tribu- 


THE    LIVER  309 

tary  to  the  portal  vein.  Corresponding  venous  channels  return  the 
blood  from  the  distribution  of  the  superior  mesenteric  artery  to 
form  the  superior  mesenteric  vein.  This  vein  unites  with  the  splenic 
vein  to  form  the  portal  vein  that  enters  the  portal  fissure  of  the  liver. 
The  nerves  of  the  great  bowel  to  the  rectum  are  derived  from  the 
sympathetic  plexuses  around  the  roots  of  the  superior  and  inferior 
mesenteric  arteries.  Their  distribution  is  similar  to  that  of  the 
small  intestine.  The  rectum  receives  its  sympathetic  fibers  from 
the  inferior  and  hypogastric  plexuses.  Its  cerebrospinal  nerves  are 
derived  from  the  second,  third  and  fourth  sacral  segments  of  the 
spinal  cord. 

THE  LIVER  (HEPARi 

The  liver  is  the  largest  gland  in  the  body,  weighing  from  50  to  55 
ounces  (1500  to  1650  grams)  in  the  male,  and  from  43  to  48  ounces 
(1290  to  1440  grams)  in  the  female.  It  represents  one-eighteenth  to 
one-twentieth  of  the  body  weight  at  birth  and  about  one-fortieth 
in  the  adult.  The  bulk  of  the  liver  lies  in  the  right  hypochondriac 
region,  the  remainder  extending  across  the  epigastric  into  the  left 
hypochondriac  region.  It  is  soft,  of  a  reddish-brown  color  and  quite 
friable.  It  is  not  completely  invested  with  peritoneum,  having  a 
large  area,  the  uncovered  area,  uninvested.  Its  shape  is  irregular 
and  inconstant  in  the  same  body  varying  under  different  conditions. 
It  is  usually  described  as  a  "right  angle  triangular  prism  with  the 
basal  angles  rounded."  Its  measurements  are  as  follows:  greatest 
transverse  7  to  8  inches  (17.5  to  20  cm.) ;  vertical  (near  the  right  side) 
6  to  7  inches  (15  to  17.5  cm.);  dorsoventral  (in  the  thickest  part) 
4  to  5  inches  (10  to  12.5  cm.). 

It  presents  five  surfaces,  superior,  ventral,  right,  dorsal  (these  four 
constituting  the  parietal  surface)  and  inferior  [visceral)  surface  and 
an  inferior  border. 

The  superior  surface  (fades  superior)  is  convex  from  before 
backward  and  slightly  concave,  to  the  left  of  the  midline,  from 
side  to  side.  This  depressed  area  is  the  cardiac  impression,  for 
here  the  heart  rests  upon  the  liver  separated  therefrom  by  the  central 
tendon  of  the  diaphragm.  The  convexity  of  the  two  sides  is  due  to 
the  doming  of  the  diaphragm.  This  surface  is  divided  by  the  sus- 
pensory ligament  into  a  greater,  right,  and  a  lesser,  left  portion. 

The  ventral  surface  is  extensive  and  of  a  triangular  shape;  it 
is  slightly  convex,  or  flattened,  resting  against  the  diaphragm  and 
the  ventral  abdominal  wall.  It  is  divided  by  the  suspensory  liga- 
ment as  above  stated.  The  right  lateral  surface  is  convex  and 
triangular  in  shape  and  rests  against  the  diaphragm. 

The  dorsal  surface  ( fades  posterior)  is  convex,  the  greater  right 
portion  being  broad  while  the  lesser  left  portion  is  narrow  and  comes 


310  THE    ALIMENTARY    TRACT 

to  a  point.  To  the  left  of  the  midline  of  the  liver  is  the  deep  vertebral 
groove  where  the  liver  is  moulded  around  the  protruding  vertebra 
column.  The  greater  portion  of  this  surface  is  uninvested  with 
peritoneum  and  is  called  the  uncovered  area.  This  area  is  from  2  to  3 
inches  (5  to  7.5  cm.)  from  above  downward  to  4  to  5  inches  (10  to 
12.5  cm.)  from  side  to  side.  This  surface  presents  from  right  to 
left,  the  uncovered  area  with  the  adrenal  impression  (impressio 
suprarenalis),  the  fossa  for  the  inferior  vena  cava  (fossa  vena  cava:), 
the  base  of  the  caudate  lobe,  the  fissure  for  the  ligamcntum  venosum  and 
the  esophageal  groove  (impressio  esophagea). 

The  inferior,  or  visceral  surface  (fades  inferior),  presents  from 
right  to  left  the  following:  Starting  across  the  upper  part  is  seen  first 


.    -  I      Suspensory  ligament 

V."  ^^^^7  Round  ligament 

^H  Wm^      J  Umbilical  notch 

^^1     jf^r  Gall-bladder 

Fig.  225. — Ventral  and  right  surfaces  of  the  liver.     {From  a  photograph.) 

the  large  renal  impression  (impressio  renalis),  then  the  transverse,  or 
portal  fissure  with  the  processus  caudatus  of  the  caudate  lobe  above  it ; 
then  the  fissure  for  the  ligamentum  venosum  (fossa  ductus  venosi) ; 
next  the  omental  tuberosity  (tuber  omentalc)  that  fits  into  the  lesser 
curvature  of  the  stomach;  lastly,  the  gastric  impression  (impressio 
gaslrica)  that  accommodates  the  ventral  surface  of  the  stomach. 
Across  the  lower  part  of  this  surface  (right  to  left)  are  seen:  first,  the 
colic  depression  (impressio  colica)  below  the  renal  impression;  the 
duodenal  depression  (impressio  duodenalis)  above  and  to  the  left; 
next,  the  gall-bladder  in  its  fossa  (fossa  vesica  fellea);  then,  the  quad- 
rate lobe  with  the  pyloric  depression  (impressio  pyloris);  the  umbilical 
fissure  for  the  round  ligament;  and  lastly,  the  end  of  the  gastric 
impression. 


THE    LIVER 


3" 


The  inferior  border,  or  margin  of  the  liver  is  sharp  and  thin. 
Where  the  falciform  ligament  reaches  it  there  is  a  deep  notch  called 
the  umbilical  notch  (incisure  umbilicalis)  which  represents  the  begin- 
ning of  the  umbilical  fissure.  A  little  to  the  right  of  the  notch  is 
seen  the  base  of  the  gall-bladder. 

The  lobes  of  the  liver  are  four  in  number,  right  (lobus  dexter)  with 
its  subdivisions  the  quadrate  (lobus  quadratus) ,  caudate  (lobus  cauda- 
tus)  and  lastly  the  left  lobe  (lobus  sinister).  The  fissures  a.re  five  in 
number  and  form  a  broken  letter  H.  Upon  the  left  are  the  continu- 
ous umbilical  (  fossa  umbilicalis)  and  ligamentum  venosum  (fossa 
ligamentum  venosum)  fissures  that  constitute  the  great  longitudinal 
fissure.       On   the   right  are   the  fissure   (fossa)  for  the  ga'l  bladder 

Inferior  i 
Caudate  lobe 
.  Esophageal  groove  \  Uncovered 

Fissure  for  the  1 


Gastric 
pression 


Omental  tuberosit 

Hepatic  arcerv 

//        ' 
Fissure  for  the  round  lig. 

Quadrate  lobe 

Gall-bladder 


gall-bladder 
Portal  fissure 


Common  duct 


Fig.   226. — Dorsal  and  inferior  surfaces  of  the  liver.     {From  a  photograph.) 

(fossa  vesica  fellece)  and  the  fissure  for  the  inferior  vena  cava  (fossa 
vena-  cava-)  interrupted  by  the  caudate  process;  connecting  the  longi- 
tudinal fissure  with  the  fossa  for  the  gall-bladder  is  the  transverse, 
or  portal  fissure  (porta  hepatica).  At  the  portal  fissure  the  hepatic 
artery,  nerves  and  portal  vein  enter  and  the  hepatic  ducts  and  lymph 
channels  pass  out. 

The  ligaments  are  the  suspensory,  coronary,  right  and  left  lateral, 
umbilical  and  ligamentum  venosum.  The  falciform,  or  suspensory 
ligament  (ligamentum  falciforme  hepalis),  is  a  sickle-shaped  fold  of 
peritoneum  that  connects  the  liver  to  the  diaphragm  and  ventral 
abdominal  wall.  It  starts  at  the  umbilicus,  passes  upward  to  the 
diaphragm  and  liver  and  then  back  to  the  dorsal  surface  where  its 


312 


THE    ALIMENTARY    TRACT 


two  layers  separate,  one  going  to  the  right  and  the  other  to  the  left 
as  the  upper  leaflets  of  the  coronary  ligament.  It  passes  over  the 
ventral  surfaces  and  superior  wall  to  the  left  of  the  midline  of  the 
liver  and  separated  the  right  from  the  left  lobes  here. 

The  coronary  ligament  (lig.  corinarium  hcpatis)  consists  of  upper 

and  lower  leaflets.     The  upper  have  been  mentioned  above.     The 

lower  leaflet  represents  the  peritoneum  from  the  visceral  surface  of  the 

liver  and  it  bounds  the  inferior  margin  of  the  uncovered  area.     At  the 

right  edge  of  the  uncovered  area  the  two  leaflets  unite  and  pass  to  the 

^^^mmmm^  .   diaphragm  as  the  right  triangular 

ligament  dig.  triangular e  dextrum). 

^djMkfe  To  the  left  of  the  caudate  lobe  the 

two  leaflets  unite  and  extend  along 

the  dorsal  edge  of  the  left  lobe  to 

its  end  and  then  to  the  diaphragm 

as  the  left  triangular  ligament  (lig. 

triangulate  sinistrum). 

The  round  ligament  (lig.  teres 
hepalis)  represents  the  impervious 
umbilical  vein  of  the  fetus  and  it 
lies  in  the  free  edge  of  the  falciform 
ligament  and  enters  and  lies  in 
the  fissure  for  the  round  ligament 
in  the  inferior  surface. 

The  ligamentum  venosum  lies  in 
the  fissure  of  that  name  and  ex- 
tends from  the  portal  fissure  dor- 
sally  to  the  inferior  vena  cava.  It 
represents  the  impervious  ductus 
i*J  venosus. 
«r  upon        The    blood-vessels    entering    the 

{From     a  . 

liver  are  the  hepatic  artery  and 
the  portal  vein.  The  latter  is  the 
real  nutrient  vessel  of  the  liver  as  it  is  laden  with  the  nutritious  sub- 
stances absorbed  from  the  gastrointestinal  tract  and  comes  into 
very  intimate  relation  with  the  hepatic  cells. 

The  several  hepatic  veins  drain  the  liver  and  empty  the  blood  into 
the  inferior  vena  cava  at  the  dorsal  surface  of  the  liver.  Two  of 
these  veins  are  usually  of  considerable  size. 

The  nerves  are  chiefly  sympathetic  from  the  celiac  plexus;  the 
cerebrospinal  nerve  assisting  is  the  left  vagus. 

To  outline  the  liver  upon  the  ventral  abdominal  wall  four  points 
are  taken:  (i)  in  the  middle  of  the  fifth  interspace  on  the  right  mid- 
clavicular line;  (3)  the  upper  margin  of  the  sixth  left  rib  li  inch 
(1  cm.)  medially  from  the  midclavicular  line;  (2)  >£  inch  (12.5  mm.) 


Fig.  227. — Outline  of  th 
the  ventral  abdominal  wa 
photograph.) 


THE    GALL-BLADDER    AND    DUCTS 


313 


below  the  tip  of  the  tenth  right  rib;  (4)  a  point  midway  be- 
between  the  lower  end  of  the  gladiolus  sterni  and  the  umbilicus  in 
the  midsternal  line.  The  line  connecting  (1)  and  (3)  should  be 
depressed  in  the  midsternal  area  representing  the  cardiac  depression. 
The  line  connecting  (1)  and  (2)  should  describe  a  curve  to  the  right. 
The  line  connecting  (3)  and  (2)  is  concavoconvex,  passes  through 
the  midsternal  point  (4)  and  is  like  a  reversed  italic  /.  The  posi- 
tion of  the  liver  varies  with  the  movements  of  respiration,  ascending 
during  expiration  and  descending  during  inspiration. 

THE  GALL-BLADDER  AND  DUCTS 

The  gall-bladder  (vesica  fellea)  lies  in  a  fossa  on  the  visceral  surface 
of  the  right  lobe  of  the  liver.     It  is  pear-shaped,  measures  about  3 


X 


C«Si«£uit      t  V      N     f  /fcCir,c 

-  ?•    -  u,„,       »»«r 

V.    \_'_   Omen. 

aie-  — 


Fig.   228.—  Structures  in  the  lesser  omentum  (liver  raised).      The  duodenum  is  laid  open  to 
show  where  the  conjoined  ducts  empty.     PV,  Portal  vein. 

inches  (7.5  cm.)  in  length  and  1  to  i}4  inches  (2.5  to  3.5  cm.)  in 
diameter.  Its  capacity  is  from  1  to  ixi  ounces  (30  to  45c.  a).  Itcon- 
sists  of  a. fundus,  body  (corpus)  and  neck  (collum).  The  neck  presents 
a  peculiar  curve  with  the  convexity  directed  toward  the  right. 

The  hepatic  duct  (ductus  hepaticus)  is  made  up  of  the  right  and 
smaller  left  lobar  ducts.  It  measures  usually  1  to  i}i  inches  (2.5 
to  3  cm.)  in  length  and  3  to  4  mm.  in  diameter  and  joins  the  cystic 
duct. 

The  cystic  duct  (ductus  cysticus)  begins  at  the  neck  of  the  gall- 
bladder and  is  from  1%  to  iH  inches  (3  to  3.75  cm.)  in  length  and 


3M 


THE    ALIMENTARY    TRACT 


3  to  4  mm.  in  diameter.     It  joins  the  hepatic  duct  to  form  the  com- 
mon bile  duct. 

The  common  bile  duct  (ductus  cholidochus)  is  about  $y2  to  4  inches 
(8.5  to  10  cm.)  in  length,  6  to  7  mm.  in  diameter  and  passes  into  the 
duodenal  wall  where  it  joins  the  pancreatic  duct.  These  ducts  pass 
obliquely  through  the  coats  of  the  duodenum  and  before  opening 
into  the  lumen  of  this  organ  there  is  a  dilatation  of  this  combined 
duct  called  the  ampulla  of  Voter.  The  orifice  of  the  common  duct  is 
2,Vi  to  4  inches  from  the  pylorus  along  the  dorsomedial  wall. 

The  gall-bladder  receives  its  blood  from  the  cystic  artery,  a  branch 
of  the  hepatic  artery.  Its  veins  empty  directly  into  the  portal  vein. 
The  nerves  are  derived  from  the  sympathetic  plexus  upon  the  hepatic 
artery. 

THE  PANCREAS 

The  pancreas  is  often  referred  to  as  the  abdominal  salivary  gland. 
When  fixed  in  situ  it  measures  from  5  to  6  inches  (12.5  to  15  cm.)  in 


Fig.  229. — Ventral 


,  pancreas  and  the  neighboring  organs. 


length.  Its  weight  is  from  85  to  90  grams.  Most  of  the  organ  lies  in 
the  epigastrium  and  the  remainder  in  the  left  hypochondrium.  It 
consists  of  head,  neck,  body  and  tail. 

The  head  (caput)  is  the  largest  portion,  measures  about  2  inches 
(5  cm.)  across.  It  lies  in  the  concavity  of  the  duodenum.  The  neck 
(collum)  is  the  narrow,  constricted  portion  between  the  head  and  the 
body.     It  is  about  1  inch  (2.5  cm.)  long  and  \'2  inch  (12  mm.)  thick. 


THE    PANCREAS  315 

The  body  (corpus)  is  the  longest  and  thickest  division  and  is  somewhat 
wedge-shaped.  It  presents  three  surfaces,  ventral,  inferior  and  dorsal, 
and  three  borders,  ventral,  superior  and  inferior.  The  tail  (cauda)  is 
the  pointed  extremity  that  extends  to  the  spleen.  The  pancreas  is 
classed  as  a  retroperitoneal  organ. 

The  pancreatic  duct  {ductus  pancreaticus)  begins  near  the  tip  of 
the  tail  and  continues  in  a  zigzag  manner  through  the  long  axis  of 
the  organ;  near  the  head  it  bends  downward  to  join  the  common  bile 
duct. 

Occasionally  an  accessory  duct  (ductus  pancreaticus  accessorius)  is 
found.  This  is  small  and  opens  independently  into  the  duodenum 
about  3i  inch  above  and  a  little  ventral  to  the  preceding  duct. 

The  arteries  are  the  superior  pancreaticoduodenale  (from  the 
gastroduodenale  of  the  hepatic  artery),  the  inferior  pancreaticoduo- 
denale (from  the  superior  mesenteric  artery)  and  pancreatic  branches 
from  the  splenic  and  hepatic  arteries.  The  veins  empty  into  the 
superior  mesenteric,  splenic  and  portal  veins.  The  nerves  are  mainly 
sympathetic  from  the  solar  plexus  by  way  of  the  celiac,  splenic  and 
superior  mesenteric  plexuses. 


CHAPTER  VIII 


THE  URINARY   SYSTEM 


The  urinary  system  comprises  the  ti 
bladder  and  the  urethra. 

THE  KIDNEYS 


'ii   kidneys,  two  ureters,   the 


Each  kidney  (re»)  is  a  large,  bean-shaped  organ,  measuring  4>2 
inches  (11.5  cm.)  in  length,  2  inches  (5  cm.)  in  width  and  about  1 '  2 
inches  (3  cm.)  in  thickness.  In  the  male  the  kidney  weighs  from 
41-2'  to  6  ounces  (135  to  180  grams)  and  in  the  female  from  4  to  5!^ 
ounces  (120  to  165  grams).  It  is  rather  solid  in  texture  and  of  a 
reddish-brown  color. 

Surfaces. — The  kidney  presents  ventral  and  dorsal  surfaces,  media! 
and  lateral  borders  and  superior  and  inferior  poles. 


Fig.   230. — Ventral  surfaces  of  the  kidneys  showing  the  areas  of  each. 

The  ventral,  or  visceral  surface  (fades  ventralis),  is  convex  and 
looks  forward  (ventrally)  and  outward.  Upon  each  kidney  are  areas 
as  follows:  Right  kidney:  adrenal,  duodenal,  hepatic  and  colic. 
Left  kidney:  adrenal,  gastric,  pancreatic,  splenic,  jejunal  and  colic. 

The  dorsal,  or  parietal  surface  (fades  dorsalis)  is  directed  backward 
(dorsally)  and  inward  and  is  flatter  than  the  ventral  surface.  The 
dorsal  surface  is  in  contact  with  muscles.  The  areas  are  diaphrag- 
316 


THE    KIDNEYS 


317 


matic,  transversalis,  quadratus  lumborum  and  psoas;  these  are  on 
both  kidneys  but  not  to  the  same  extent.  In  addition  to  these, 
upon  the  left  kidney  may  be  seen  two  grooves  formed  by  the  eleventh 
and  twelfth  ribs  and  two  little  depressions  near  the  medial  border 
formed  by  the  transverse  processes  of  the  first  and  second  lumbar 
vertebrae,  respectively.  On  the  right  kidney  there  is  one  groove 
formed  by  the  twelfth  rib  and  one  depression  formed  by  the  trans- 
verse process  of  the  first  lumbar  vertebra. 

The  lateral  border  {mar go  lateralis)  is  convex  in  both  directions  and 
belongs  more  to  the  dorsal  surface.  The  medial  border  {margo 
medialis)  is  concave  presenting  a  deep  notch,  the  kilns,  seen  mainly 
from  the  front.  The  vessels  here  are  the  renal  vein,  in  front,  the 
renal  artery,  above  and  in  the  middle,  and  the  ureter  behind  and 
below. 


Fig.   231. — Dorsal  surfaces  of  the  kidneys  showing  the  areas  of  each. 

The  superior  pole,  or  extremity  is  thick  and  broad  and  about  4  cm. 
from  the  midline.  It  is  capped  by  the  adrenal.  The  inferior  pole, 
or  extremity  is  usually  thinner  and  more  pointed  than  the  preceding 
and  is  about  5J2  cm.  from  the  midline  of  the  body. 

If  the  kidney  be  sectioned  longitudinally,  and  parallel  to  the  sur- 
faces, a  number  of  important  points  are  noted.  The  peripheral  one- 
third  is  distinctly  demarcated  from  the  inner  two-thirds  and  these 
constitute  the  cortex  and  medulla,  respectively.  The  cortex  (sub- 
stantia (corticalis)  shows  striations  perpendicular  to  the  surface. 
These  alternating  dark  and  light  stripes  are  due  to  the  difference  in 
vascularity  of  these  two  parts:  the  dark  ones  constitute  the  labyrinth 
(pars  convoluta)  and  are  the  more  vascular;  the  lighter  ones  are  the 
medullary  rays  (pars  rod  iota).  The  rays  are  continuous  with  the 
medullary  portion  of  the  kidney  while  the  labyrinth  extends  a  dis- 


3i* 


THE    URINARY    SYSTEM 


tance  into  the  medulla  between  the  medullary  pyramids,  forming  here 
the  cortical  ends  of  the  columns  of  Berlin  or  columna  renales. 

The  medulla  {substantia  medidlaris)  is  seen  to  consist  of  a  number 
of  pyramids  (pyramides  renales)  the  apices  of  which  are  directed 
toward  the  sinus  and  the  bases  (bases  pyramides)  toward  the  cortex. 
The  basal  areas  constitute  the  boundary  zone  of  the  kidney.  Between 
the  pyramids  are  the  incomplete  fibrous  columns  of  Berlin  (columna; 
renales)  the  pathways  of  the  vessels  to  and  from  the  boundary 
zone. 

Just  within  the  hilus  is  seen  an  area  called  the  sinus.  This  is 
occupied  by  the  pelvis  of  the  ureter  and  the  branches  of  the  renal 
artery,  the  tributaries  of  the  renal  vein  and  some  adipose  tissue. 
Here  are  also  seen  the  apices  of  the 
medullary  pyramids  that  project 
into  the  sinus  a  short  distance  con- 
stituting the  papilla  renales. 

The  kidneys  are  retroperitoneal, 
that  is,  not  in  any  way  or  part  in- 
vested with  peritoneum.  Each  is 
usually  imbedded  in  considerable  fat, 
Hi/u*s  the  fatty  capsule  (capsitla  adiposa) 
wihch  is  usually  thicker  at  the 
margins  of  the  organ.  In  this  fatty 
tissue  is  seen  the  fascia  renalis,  a 
sheet  of  white  fibrous  tissue  with 
some  fat  interposed  between  it  and 
the  kidney  (the  perirenal  fat). 
That  portion  of  the  fatty  capsule 
outside  of  the  renal  fascia  is  the 
pararenal  fat.  The  organ  is  held  in 
position  by  the  surrounding  organs, 
chiefly,  and  somewhat  by  the  renal 
fascia. 

The  vessels  of  the  kidney  are  the  renal  artery  and  the  renal  vein. 
The  nerves  are  about  fifteen  in  number  and  are  derived  from  the 
renal  plexus.  This  plexus  is  formed  by  branches  from  the  solar 
plexus,  celiac  ganglion,  aortic  plexus  and  lesser  and  least  splanchnic 
nerves.  Branches  from  the  tenth,  eleventh  and  twelfth  thoracic 
nerves  also  reach  the  kidneys. 

The  kidneys  lie  mainly  in  the  epigastric  and  umbilical  regions  but 
extend  somewhat  into  the  lumbar  and  hypochondriac  regions.  The 
left  is  usually  higher  than  the  right.  The  left  kidney  extends  from 
the  middle  of  the  eleventh  thoracic  vertebra  to  the  upper  border  of 
the  third  lumbar  vertebra.  The  right  kidney  extends  from  the  lower 
border  of  the  eleventh  thoracic  vertebra  to  the  middle  of  the  third 


Fig.  232. — Median  longitudinal  section 
of  the  right  kidney.  A.  A,  Calyces 
minores;  B,  B,  calyces  majores;  C,  pelvis 
of  the  ureter;  5,  hilus  of  the  kidney. 


THE    URETERS 


319 


lumbar  vertebra.  In  the  female  they  are  somewhat  lower  than  in  the 
male.  The  inferior  poles  are  il4,  to  2  inches  (3.75  to  5  cm.)  above 
the  crests  of  the  ilium.  The  upper  pole  of  each  is  4  cm.  from  the  mid- 
line while  the  lower  pole  is  5^  cm.  from  the  midline. 

THE  URETERS 

The  ureters  are  the  tubes  by  means  of  which  the  urine  is  con- 
veyed from  the  kidneys  to  the  bladder.  Each  consists  of  a  pelvis 
and  ureter  proper.  The  pelvis  lies  in  the  sinus  and  consists  of  a  num- 
ber of  small  divisions,  the  calyces  minores  eight  to  ten  in    number. 


•  of  a  corrosion  preparation  of  the 
(From  a  photograph.) 


ssels  and  ureter  of  the  kidney. 


These  calyces  minores  surround  and  are  completely  attached  to 
two  or  three  pyramid  apices  and  join  to  form  two  or  three  tubular 
structures,  the  calyces  major es.  The  junction  is  somewhat  enlarged 
and  constitutes  the  pelvis.  At  the  level  of  the  disc  between  first  and 
second  lumbar  vertebne  it  continues  as  the  ureter  proper. 

The  ureter  proper  is  a  small  tube  about  4  mm.  thick  and  10  to 
12  inches  (25  to  30  cm.)  in  length.  It  extends  from  the  upper  border 
of  the  second  lumbar  vertebra  to  the  bladder.  The  first  part  (pars 
abdominalis)  lies  in  the  abdominal  cavity  and  corresponds  nearly  to 
the  midinguinal  line.  The  second  half  (pars  pelvina)  lies  in  the  pel- 
vic cavity.  When  it  reaches  the  bladder,  it  enters  that  structure 
obliquely  and  proceeds  for  nearly  an  inch  (2.5  cm.)  between  the  mus- 
cular and  mucous  coats.  Its  opening  in  the  bladder  is  guarded  by 
mucous  folds. 


320 


THE    URINARY    SYSTEM 


Its  blood  supply  is  from  the  renal,  spermatic,  ovarian,  middle 
hemorrhoidal  and  superior  vesical  arteries.  Its  nerves  are  derived 
from  the  renal,  spermatic  and  hypogastric  plexuses  of  the  sympa- 
thetic system. 


THE  BLADDER 


The  bladder  (vesica  urinaria),  located  in  the  pelvic  cavity  just 
behind  the  symphysis  pubis,  is  the  reservoir  for  the  urine.     When 


Fig.  234. — Medii 


prostate,  urethr. 


empty  and  contracted  the  bladder  is  almost  spherical  in  shape.  Its 
shape  in  the  infant  is  somewhat  conical.  In  the  empty  collapsed 
state,  as  in  the  cadaver,  it  is  somewhat  cup-shaped.  When  dis- 
tended, it  is  about  $}$  inches  (14  cm.)  in  height,  44  inches  (11. 5  cm.) 
in  width  and  nearly  4  inches  (10  cm.)  dorsoventrally,  and  then 
extends  into  the  abdominal  cavity.  In  the  female  the  width  is 
greater  and  the  dorsoventral  dimension  less.  Its  capacity  is  about  1 
pint  (500  to  700  c.c.)  but  is  usually  emptied  when  it  contains  8  to  10 
ounces  (about  300  c.c). 


THE    BLADDER 


321 


The  bladder  presents  an  apex,  a  base,  a  superior  and  ventroinferior 

and  two  lateral  surfaces  and  illy  defined  borders. 

The  apex  (vertex  veskce)  is  best  seen  in  the  nearly  empty  bladder 
and  lies  just  behind  the  symphysis  pubis.  From  this  the  urachus 
extends  to  the  umbilicus.  The  base  (fundus  vesica)  is  directed 
downward  and  backward  (dorsally)  and  is  partly  in  relation  with 
rectum  and  seminal  vesicles  of  the  male  and  vagina  of  the  female. 
It  is  partially  invested  by  peritoneum.  The  superior  surface  is 
directed  toward  the  abdominal  cavity  and  its  shape  varies  with  the 
state  of  distention.  It  is  invested  with  peritoneum.  The  ventro- 
inferior surface  is  directed  downward  and  forward  (ventrally)  and 


Fig.   23s. — Bladder  laid  open  showing  the  trigo 


when  the  bladder  is  distended  it  is  partially  invested  with  perito- 
neum. The  so-called  neck  of  the  bladder  is  at  the  lowest  part  of  the 
organ,  at  the  junction  of  the  base  and  ventroinferior  surface.  Here 
the  urethra  begins  and  it  represents  the  most  fixed  part  of  the  blad- 
der. The  lateral  surfaces  are  directed  downward  and  outward  and 
meet  in  front  at  the  urethral  orifice.  Each  is  partially  invested  with 
peritoneum. 

When  the  empty  contracted  bladder  is  opened  the  mucosa  exhib- 
its folds,  or  rugae  except  at  the  trigone.  In  the  distended  bladder 
these  folds  disappear.  The  trigone  (trigonum  vesica)  is  a  triangular 
area  at  the  neck;  at  the  basal  angles  are  the  two  ureteral  orifices  and 


3  2  2  THE    URINARY    SYSTEM 

at  the  apical  angle  is  the  urethral  orifice.  The  sides  are  of  equal 
length  and  measure  about  i!4  inches  (3  cm.)  in  the  empty  bladder 
and  i'2  inches  (3.75  cm.)  in  the  distended  condition.  The  ureteral 
orifices  are  usually  guarded  by  small  folds  of  the  mucosa.  Extend- 
ing upward  and  outward  from  each  ureteral  orifice  is  seen  a  short 
ridge  the  ureteral  fold  (plica  ureterica)  formed  by  the  ureter  in  its 
oblique  course  through  the  bladder  wall.  Connecting  the  ureteral 
orifices  is  another  fold  (basal  side  of  the  trigone)  the  intcrurcteral  fold 
{torus  ureterica),  extending  from  the  middle  of  the  fold  across  the 
trigone,  and  on  into  the  urethra,  is  a  ridge  the  uvula  of  the  bladder 
{uvula  vesica). 

The  ligaments  are  ten  in  number,  five  true  and  five  false.  The 
true  ligaments  are  mainly  fascial  bands  and  are  the  two  ventral,  the 
two  lateral  and  the  middle.  The  ventral  ligaments  (puboprostatic) 
extend  from  the  neck  of  the  bladder  to  the  prostate  gland  and  then 
to  each  side  of  the  symphysis  pubis.  The  lateral  ligaments  extend 
from  the  side  of  the  bladder  and  prostate  gland  to  the  lateral  walls 
of  the  pelvis.  The  middle,  or  umbilical  ligament  dig.  umbilicales 
medium),  consists  of  the  impervious  urachus  and  extends  from  the 
summit  of  the  bladder  to  the  umbilicus. 

The  false  ligaments  are  peritoneal  folds  and  are  five  in  number, 
two  dorsal,  two  lateral  and  one  ventral.  The  dorsal  false  ligaments 
extend  from  the  dorsolateral  region  of  the  bladder  to  the  side  of  the 
rectum  in  the  male;  between  the  two  there  is  a  depression  called 
the  rectovesical  pouch.  In  the  female  these  ligaments  extend  from 
the  dorsolateral  region  of  the  bladder  to  the  sides  of  the  uterus  bound- 
ing thus,  the  uterovesical  pouch.  The  lateral  false  ligaments  extend 
from  the  sides  of  the  bladder  to  the  lateral  pelvic  walls  and  iliac 
fossae.  The  ventral  false  ligament  extends  from  the  apex  of  the  bladder 
to  the  umbilicus  and  lies  over  the  urachus.  Extending  from  the 
sides  of  the  bladder  and  converging  at  the  umbilicus  are  two  addi- 
tional folds  of  peritoneum  that  cover  the  two  impervious  hypo- 
gastric, or  umbilical  arteries.  These  folds  are  the  plica  umbilicales 
laterales  and  the  impervious  arteries  are  sometimes  referred  to  as 
the  round  ligaments  of  the  bladder. 

The  arterial  supply  of  the  bladder  is  from  the  superior,  middle 
and  inferior  vesical  arteries  in  the  male;  in  the  female  other  branches 
are  received  from  the  uterine  and  vaginal  arteries.  The  veins  carry 
the  blood  to  the  tributaries  of  the  hypogastric  veins  and  anastomose 
with  the  pudendal  venous  plexus. 

The  lymphatics  are  few  and  empty  into  the  intern  aliliac,  hypo- 
gastric and  sacral  nodes. 

The  nerves  are  from  the  third  and  fourth  sacral  cerebrospinal 
nerves  through  the  vesical  plexus  and  from  the  upper  lumbar  nerves 
through  the  hypogastric  plexus. 


THE  URETHRA  323 

THE  URETHRA 

The  urethra  varies  in  the  male  and  female.  The  female  urethra 
(urethra  muliebris)  is  about  i'-2  inches  (3.75  cm.)  in  length  extending 
from  the  neck  of  the  bladder  (orificium  urethra  internum)  to  the 
external  urinary  meatus  (orificium  urethra;  externum)  in  the  vestibule. 
It  may  be  dilated  to  about  li  inch  (6  mm.)  and  lies  imbedded  in  the 
ventral  wall  of  the  vagina.     It  is  directed  downward  and  forward. 

The  male  urethra  (urethra  virilis),  7  to  8  inches  (17.5  to  20  cm.)  in 
length,  extends  from  the  neck  of  the  bladder  to  the  end  of  the  penis. 
It  consists  of  three  parts,  prostatic,  membranous  and  penile  portions. 
The  prostatic  portion  (pars  prostatica)  is  about  1  inch  (2.5  cm.)  in 
length  and  courses  through  the  prostate  from  its  base  to  its  apex. 
It  presents  the  most  dilated  part  of  the  urethra;  its  greatest  caliber 
is  12  mm.  Upon  its  dorsal  wall  or  floor  is  seen  a  ridge  the  urethral 
crest  (crista  urcthralis)  which  represents  a  continuation  of  the  uvula 
of  the  bladder.  The  middle  part  of  this  ridge  is  slightly  thickened 
and  shows  a  depression  in  the  center,  the  sinus  pocularis  (utriculus 
proslaticus)  upon  each  side  of  which  is  to  be  seen  the  opening  of  the 
ejaculatory  duct.  At  each  side  of  the  crest  is  a  linear  depression,  the 
prostatic  sinuses,  into  which  open  the  prostatic  ducts. 

The  membranous  portion  (pars  membranacea)  is  about'  M  inch 
(12  mm.)  in  length  and  lies  beneath  the  symphysis  pubis.  It  is 
firmly  fixed  in  position  and  not  easily  dilated.  Its  caliber  is  about 
8  mm. ;  its  distal  part  has  thin  walls  and  is  the  part  that  is  most  liable 
to  rupture. 

The  spongy,  or  penile  portion,  is  about  6  inches  (15  cm.)  in  length 
and  lies  in  the  spongy  portion  of  the  penis  and  glans  penis.  Its 
caliber  is  about  9  mm.  except  near  the  end  where  it  is  dilated  to 
from  12  to  14  mm.,  the  fossa  navicularis.  Its  termination  is  called 
the  external  urinary  meatus  (orificium  urethra;  externum)  and  repre- 
sents a  vertical  slit  about  Vi  inch  (6  mm.)  in  extent. 


CHAPTER  IX 
THE  MALE  ORGANS  OF  REPRODUCTION 

The  male  organs  of  reproduction  comprise  the  two  testes,  two 
vasa  deferentia,  two  seminal  vesicles,  two  ejaculatory  ducts,  a 
prostate,  two  glands  of  Cowper,  the  penis  and  the  scrotum. 


The  testes,  two  in  number,  lie  in  the  scrotum.     The  scrotum  is  a 
pouch-like  structure  of  skin  at  the  dorsal  side  of  the  root  of  the  penis. 


Spermo/tic 
Cord. 


Tunica. 

/?  /  buy  ii"-^ 


Dmitri 

T    poss«- 


Fig.  236. — The  left  testis  in  situ  with  the 
tunica  vaginalis  partly  removed. 


Fig.  237. — Frontal   section  of   testis,    epi 
didymis  and  spermatic  cord: 


It  is  divided  into  two  compartments  by  a  septum  {septum  scroti)  which 
corresponds  to  the  ridge,  or  raphe  upon  the  outside.  Internally 
each  compartment  is  lined  by  a  serous  membrane,  the  parietal  layer 
oj  the  tunica  vaginalis  testis.     This  was  derived  from  the  peritoneum 

324 


THE    SPERMATIC    CORD  325 

during  intrauterine  life.  Between  the  serous  membrane  and  skin 
is  the  dartos  (tunica  dartos)  which  contains  some  smooth  muscle 
tissue. 

Each  testis  occupies  a  compartment  and  is  suspended  by  the 
spermatic  cord.  Each  organ  is  about  i'2  to  2  inches  (4  to  5  cm.)  in 
length,  1J-4  inches  (3  cm.)  dorsoventrally  and  1  inch  (2.5  cm.)  in 
width.  It  weighs  about  1  ounce  (30  grams)  and  its  parenchyma  is 
yellowish  in  color.  The  long  axis  is  directed  forward,  upward  and 
outward. 

The  testis  presents  two  surfaces,  two  borders  and  two  poles.  The 
lateral  (fascies  lateralis)  and  the  medial  (fades  medialis)  surfaces  are 
convex  and  smooth.  The  ventral  border  (mar go  ventralis)  is  convex 
and  free.  The  dorsal  border  (margo  dorsalis)  is  somewhat  flattened 
and  has  the  epididymis  attached  to  it.  The  superior  pole,  or  ex- 
tremity is  rounded  and  to  it  is  attached  the  head  of  the  epididymis; 
to  the  inferior  pole,  or  extremity  and  lower  part  of  the  dorsal  border 
is  attached  the  gubernaculum  that  connects  the  testis  to  the  scrotum. 
The  testis  is  invested  by  the  tunica  vaginalis  testis  except  along  the 
dorsal  border  where  the  epididymis  is  attached.  Along  the  outer 
side  of  the  organ  the  serous  tunic  passes  in  between  the  testis  and 
epididymis  forming  the  digital  fossa  (sinus  cpididymi). 

The  epididymis  consists  of  the  head  (caput  epididymis),  the  body 
(corpus  epididymis)  and  the  tail  (caiida  epididymis).  The  head  and 
tail  are  attached  to  the  testis  by  the  superior  and  inferior  epididymal 
ligaments.  At  the  head  the  excretory  ducts  of  the  testicle  enter 
and  form  that  portion  of  the  epididymis.  The  body  and  tail  portions 
consist  of  the  convolutions  of  one  tubule;  if  this  tubule  be  straight- 
ened it  would  measure  about  20  feet  in  length. 

The  spermatic  cord  (funiculus  spcrmaticus)  suspends  the  testicle 
in  the  scrotum  and  serves  as  pathway  for  vessels,  nerves,  lymphatics 
and  the  vas.  It  consists  of  numerous  vessels,  white  fibrous  tissue 
and  some  muscle  tissue,  the  cremaster  muscle.  It  contains  the  vas, 
the  spermatic,  cremasteric  and  deferential  arteries,  the  pampiniform 
plexus  of  veins,  nerves  and  lymphatics.  It  extends  from  the  back  of 
the  testis  through  the  so-called  inguinal  canal  to  the  internal  abdomi- 
nal ring,  measuring  about  5  inches  (12.5  cm.)  in  length. 

The  artery  of  the  testicle  is  the  spermatic  artery,  that  is,  a  branch 
of  the  abdominal  aorta.  The  venous  channels  form  the  internal 
spermatic  vein  which  then  forms  a  complicated  plexus  upon  the 
spermatic  cord,  the  pampiniform  plexus.  This  plexus  reforms  the 
spermatic  vein  that  enters  the  abdomial  cavity  at  the  internal  ab- 
dominal ring;  the  right  one  empties  directly  into  the  inferior  vena 
cava  while  that  of  the  left  side  empties  into  the  left  renal  vein. 

The  nerves  are  derived  chiefly  from  the  tenth  thoracic  nerve 
through  the  spermatic  plexus  of  the  sympathetic  system. 


326 


THE  MALE  ORGANS  OF  REPRODUCTION 


THE  VAS  DEFERENS 

The  vas  deferens  (ductus  deferens)  the  continuation  of  the  epididy- 
mis, is  about  18  inches  (45  cm.)  in  length,  but  the  first  6  inches  are 
coiled  in  a  small  area  at  the  end  of  the  epididymis.  The  vas,  one  on 
each  side,  joins  the  spermatic  cord  and  continues  in  this  through  the 
inguinal  canal  to  the  internal  abdominal  ring;  here  it  enters  the  ab- 
dominal cavity  and  continues  into  the  pelvic  cavity,  passes  to  the 
under  surface  of  the  bladder  and  near  the  prostate  gland  is  it  joined 
by  the  seminal  duct.  Near  its  end  it  dilates  constituting  the  ampulla 
(ampulla  ductus  deferens).  It  then  becomes  smaller  and  joining  the 
seminal  duct  forms  the  ejaculatory  duct. 

THE  SEMINAL  VESICLES 

The  seminal  vesicles  (vesciculce  seminales)  are  two  rather  wide, 
convoluted  tubes  beneath  the  base  of  the  bladder.     Each  is  about 


Fig.    238. — Dorsal  view  of  distended  bladder  and  neighboring  organs  of  reproductic 


2l2  inches  (6  cm.)  in  length,  10  mm.  in  breadth  and  5  mm.  in  thick- 
ness. If  straightened  each  would  measure  about  5  inches  (12.5  cm.) 
in  length.  The  duct  (ductus  excretorius)  is  short  and  joins  the  vas 
to  form  the  ejaculatory  duct. 


THE    PROSTATE 


32/ 


Theejaculatory  duct  {ductus  ejaculatorius)  is  about  3iinch  (18  mm.) 
in  length  and  enters  the  prostate  gland  near  the  inferior  basal  angle, 
converges  with  its  fellow  of  the  opposite  side  to  the  dorsal  wall  of  the 
urethra  where  each  empties  upon  the  urethral  crest. 

THE  PROSTATE 

The  prostate  gland  {prostata)  is  a  pyramidal-shaped  organ  situated 
at  the  so-called  neck  of  the  bladder.     It  is  of  a  dark  red  color  and 


Fig.  239. —  Median  sagittal  section  through  the  bladder,  prostate,  urethra  and  penis 
of  the  male. 


musculoglandular  in  structure.  It  is  about  il-i  inches  (3.5  cm.) 
wide,  1  inch  (2.5  cm.)  thick  and  1  '4  inches  (3.5  cm.)  high.  It  weighs 
about  y2  ounce  (15  grams.) 

It  consists  of  apex,  base,  ventral,  dorsal  and  lateral  surfaces.  The 
apex  (apex  prostata-)  is  directed  downward  and  forward  and  rests 
upon  the  deep  layer  of  the  urinogenital  diaphragm.  The  base  (basis 
prostata1)  is  directed  upward  and  backward  and  is  in  contact  with  the 
bladder.  Near  the  middle  of  the  base  the  urethra  enters  the  organ 
and  courses  through  it  to  the  apex.     At  the  inferior  angles  of  the 


328  THE  MALE  ORGANS  OF  REPRODUCTION 

base  the  ejaculatory  ducts  enter  the  organ  and  converge  at  the 
urethra.  That  portion  of  the  prostate  between  these  ducts  and  the 
urethra  constitutes  the  so-called  middle  lobe  of  the  prostate. 

The  dorsal  surface  (fades  posterior)  is  in  contact  with  the  rectum. 
The  ventral  surface  (fades  anterior)  is  directed  toward  the  symphysis 
pubis  and  is  connected  to  it  by  the  two  puboprostatic  ligaments. 
The  lateral  surfaces  (fades  laterales)  are  in  contact  with  the  leva- 
tores  ani  muscles  with  only  a  venous  plexus  intervening. 

The  visceral  layer  of  the  pelvic  fascia  invests  the  prostate  upon  its 
lateral  and  dorsal  surfaces;  this  is  called  the  sheath  of  the  prostate. 
It  is  continuous  at  the  apex  of  the  gland  with  the  urinogenital  dia- 
phragm and  from  its  ventral  part  two  bands  continue  to  the  pubis  as 
the  puboprostatic  ligaments. 

The  arteries  of  the  prostate  are  derived  from  the  middle  hemor- 
rhoidal, internal  pudic  and  inferior  vesical  arteries.  The  veins  form 
a  plexus  around  the  gland  and  then  empty  into  the  hypogastric 
(internal  iliac)  veins.  In  elderly  male  these  veins  are  usually  en- 
larged. The  nerves  are  from  the  hypogastric  plexus  of  the  sympa- 
thetic system. 

COWPER'S  GLANDS 

The  glands  of  Cowper  are  located  between  the  layers  of  the  tri- 
angular ligament  and  their  ducts  empty  into  the  penile  urethra. 
They  are  small  organs  about  6  to  8  mm.  in  diameter.  The  duct  of 
each  is  about  1  inch  (2.5  cm.)  in  length. 

THE  PENIS 

The  penis  is  attached  to  the  pubic  arch.  It  is  composed  chiefly  of 
erectile  tissue.  In  the  pendulous  state  the  surfaces  are  under,  or 
urethral,  and  the  opposite  surface  is  the  dorsum.  It  consists  of  root, 
bodv  and  glans  penis.  The  root  (radix  penis)  consists  of  two  crura 
and  a  bulb.  Each  crus  arises  from  the  side  of  the  pubic  arch,  gradu- 
ally increasing  in  size  and  continuing  as  the  corpus  cavernosum. 
Each  crus  is  surrounded  by  the  ischiocavernosus  muscle  and  con- 
verges to  meet  its  fellow  at  the  midline.  The  bulb  (bulbus  urethra:) 
is  the  beginning  of  the  corpus  spongiosum  and  lies  behind  the  point 
at  which  the  urethra  enters  the  corpus  spongiosum. 

The  body  (corpus  penis)  of  the  penis  consists  of  two  corpora  cav- 
ernosa (corpora  cavernosa  penis)  and  the  corpus  spongiosum  (corpus 
cavernosum  urethra?).  Each  corpus  cavernosum  lies  to  the  side  of  the 
midline  of  the  organ  in  the  dorsal  part  of  the  penis  and  consists  of 
erectile  tissue.  The  corpus  spongiosum  lies  in  a  groove  upon  the 
under  surface  of  the  corpora  cavernosa.  It  is  traversed  by  the 
urethra  and  consists  of  erectile  tissue.  These  three  structures  are 
surrounded  by  white  fibrous  tissue  and  the  loose  skin. 


THE    PENIS 


329 


The  glans  penis  is  the  continuation  of  the  corpus  spongiosum  and 
is  an  expanded,  cap-like  structure  that  covers  the  ends  of  the  corpora 
cavernosa,  where  its  edge  is  raised  forming  the  corona  gland  is.  At  its 
end  is  a  slit-like  orifice  the  external  urinary  meatus.  On  the  glans  the 
skin  forms  a  free  covering,  or  hood,  the  prepuce  (prcputinm )  that  is 
attached  to  the  glands  beneath  the  urinary  meatus  by  a  delicate 
fold,  the  frenulum  {frenulum  prcputii).     From  the  fibrous  capsule  of 


Fig.  240. — Male    organs    of 
(except  testes). 


Fig.  241. —  Male  urethra  laid  open.  A, 
Urethral  crest;  B,  prostate;  C.  glands  of 
Cowper;  D,  bulb;  E.  fossa  navicularis;  F, 
external  urinary  meatus. 


the  penis  a  triangular  fold  of  fibrous  tissue  is  attached  to  the  sym- 
physis pubis;  it  is  the  suspensory  ligament  (ligamentum  suspensorium 
penis)  of  the  penis.  Between  the  capsule  and  the  corpora  cavernosa 
lie  the  dorsal  vein  and  dorsal  arteries  of  the  penis. 

The  arteries  that  supply  the  penis  are  deep  dorsal  arteries  and  the 
artery  to  the  bulb.  The  veins  empty  into  the  prostatic  plexus  or  into 
the  dorsal  vein. 

The  nerves  are  from  the  pudenal  nerve  and  hypogastric  and 
pelvic  plexuses  of  the  sympathetic  system. 


CHAPTER  X 
THE  FEMALE  ORGANS  OF  REPRODUCTION 

The  female  organs  consist  of  the  two  ovaries,  two  oviducts,  uterus, 
vagina,  internally,  and  the  two  glands  of  Bartholin,  the  vestibule, 
clitoris,  hymen,  two  labia  minora  and  two  labia  majora  and  mons 
veneris,  externally. 

The  ovaries  lie  at  the  side  of  the  pelvic  cavity  in  a  little  depression 
called  the  ovarian  fossa  (fossa  ovarica).  They  lie  behind  the  broad 
ligament  of  the  uterus  and  are  attached  thereto.  Each  organ  is 
about  ili  inches  (3.75  cm.)  long,  *i  inch  (18  mm.)  wide  and  \i  inch 


Body 


Fimbriated  extremity 


Fig.   242. — Dorsal 


and   broad   ligament  sho 
n  (i  photograph.) 


(8  mm. )  thick.  It  weighs  about  4  to  8  grams.  Each  presents  two 
surfaces,  two  borders  and  two  poles.  The  long  axis  is  directed  down- 
ward (caudad)  and  medially. 

The  pelvic,  or  lateral  (fades  lateralis)  and  visceral,  or  medial  sur- 
faces (fades  medialis)  are  convex  and  nodular;  the  latter  condition  is 
due  to  the  projecting  Graafian  follicles,  between  the  age  of  puberty 
and  the  menopause.  The  dorsal  border  (margo  liber)  is  convex  and 
free.  The  ventral  border  (margo  mesovaricus)  is  not  free  and  repre- 
sents the  attached  border;  it  is  connected  to  the  broad  ligament  by  a 
double  sheet  of  peritoneum,  the  mesovarium.  The  superior,  or 
tubal  pole  (e.xlremilas  tubaria)  is  rounded  and  covered  by  the  fim- 
330 


THE    OVIDUCTS  33  I 

briated  extremity  of  the  oviduct;  one  of  the  largest  fimbria?  is 
attached  to  the  ovary  and  is  called  the  ovarian  fimbria  {fimbria 
ovarica).  The  inferior,  or  uterine  pole  {extremitas  uterina)  is  directed 
toward  the  uterus  and  is  connected  to  it  by  a  cylindric  band  of 
fibrous  tissue,  the  uteroovarian  ligament  (ligamcntum  ovarii  proprium). 
The  ovary  is  connected  to  the  lateral  pelvic  wall  by  a  triangular  fold 
of  peritoneum,  the  suspensory  ligament  (ligament  sitspensorium 
ovarii)  through  which  the  vessels  gain  access  to  the  ovary. 

The  ligaments  of  the  ovary  are  the  mesovarium,  suspensory, 
uteroovarian  and  the  fimbria  ovarica. 

The  arteries  of  the  ovaries  are  the  ovarian  from  the  abdominal 
aorta.  These  enter  at  the  hilus  with  the  branches  of  the  uterine 
artery.  The  veins  form  first  a  plexus  similar  to  the  pampiniform 
plexus  of  the  male,  near  the  ovary,  and  then  form  the  ovarian  vein 
upon  each  side.  The  right  one  empties  into  the  inferior  vena 
cava  while  the  left  one  empties  into  the  left  renal  vein. 

The  nerves  are  from  the  ovarian  plexus  continuous  with  the  renal 
and  aortic  plexuses  of  the  sympathetic  system;  sensor  fibers  from 
the  ovary  pass  through  the  dorsal  root  of  the  tenth  thoracic  nerve. 

THE  OVIDUCTS 

Each  oviduct  {tuba  uterina)  is  about  4  inches  (10  cm.)  long  and 
extends  from  the  ovary  to  the  uterus.  It  is  situated  at  the  upper 
border  of  the  broad  ligament  in  the  pelvic  cavity  and  is  not  straight 
in  course.  Each  consists  of  an  infundibulum.  the  ampulla  and 
isthmus. 

The  infundibulum  {infundibulum  tuba:  uterina)  or  fimbriated 
extremity  is  funnel-shaped  and  fringed;  this  fringe  constitutes  the 
fimbriae  and  one  of  these  fimbria?  is  attached  to  the  ovary.  Its 
opening  {ostium  abdominale)  is  about  2  mm.  in  diameter.  The 
ampulla  (ampulla  tuba  uterina;)  is  the  longest,  widest  and  most  tor- 
tuous portion;  its  first  part  is  hooked  over  the  superior  pole  of  the 
ovary.  The  isthmus  (isthmus  tuba  uterina),  the  narrowest  part,  is 
straight  and  horizontal  in  its  course  and  ends  at  the  lateral  angle  of 
the  uterus.  Its  opening  (ostium  uterinum  tuba)  is  1  mm.  in  diameter. 
It  has  a  thick  wall. 

The  oviduct  is  connected  to  the  upper  part  of  the  broad  ligament 
of  the  uterus  by  a  thin  band  of  peritoneum,  the  mesosalpinx.  The 
tube  is  entirely  invested  with  peritoneum. 

The  blood  supply  is  from  the  ovarian  and  mainly  the  uterine 
arteries.  The  veins  empty  into  the  uterine  and  ovarian  veins.  The 
nerves  are  from  the  ovarian  and  uterine  plexuses  of  the  sympathetic 
system.  Its  sensor  fibers  enter  the  dorsal  roots  of  the  eleventh  and 
twelfth  thoracic  and  first  lumbar  nerves. 


332 


THE  FEMALE  ORGANS  OF  REPRODUCTION 


THE  UTERUS 


The  uterus,  or  womb,  is  a  muscular  organ  with  a  very  small  cavity. 
It  is  situated  in  the  pelvic  cavity.  It  is  of  a  flattened  pear-shape 
and  its  walls  are  very  thick.  Its  position  varies  with  the  position 
of  the  body  and  the  state  of  the  bladder  and  the  rectum.  It  meas- 
ures (in  the  virgin)  3  inches  (7.5  cm.)  in  length,  2  inches  (5  cm.)  in 
width  and  1  inch  (2.5  cm.)  in  thickness.  In  the  virgin  it  weighs 
about  1 V2  ounces  (45  grams)  and  in  those  that  have  borne  children 
about  2H  ounces  (75  grams).  It  consists  of  fundus,  body,  cervix  and 
lateral  border. 


-Dorsal  view  of  the  uterus  ; 
broad  ligament. 


nd  left  half  of  the 


Fig.  244. — Frontal  section 
tirough  the  uterus  showing  its 
avity  (diagrammatic),  C, 
licse  palmatae. 


The  fundus  (Jundus  uteri)  is  the  upper,  broad  and  convex  extrem- 
ity above  the  level  of  the  openings  of  the  oviducts  and  represents 
about  li  inch  of  the  length.  The  body  {corpus  uteri)  is  somewhat 
triangular  in  shape,  broad  above  and  narrower  below.  Its  ventral 
surface  {fades  vesicalis)  is  flattened  while  the  dorsal  surface  {fades 
intestinalis)  is  convex.  At  the  sides  the  broad  ligaments  of  the 
uterus  are  attached.  It  represents  about  1%  inches  of  the  length 
of  the  uterus.  The  cervix,  or  neck  {cervix  uteri)  about  1  inch  in 
length,  is  cylindrical  in  shape.  It  connects  the  body  of  the  uterus 
with  the  vagina.  The  lower  end  projects  into  the  vagina  and  consti- 
tutes the  vaginal  portion  {portio  vaginalis),  while  the  upper  end  is 
called  the  supravaginal  part  {portio  supravaginalis). 

The  cavity  of  the  uterus  when  seen  from  the  side  represents  a 
mere  slit.  Viewed  from  the  front,  that  part  in  the  body  is  triangular 
in  outline  and  the  cervical  portion  (canal)  is  spindle-shaped.  The 
upper  end  of  the  cervical  canal  {canal is  cervicis  uteri)  represents  the 
internal  OS  (orijicium  internum  uteri)  while  the  vaginal  end  repre- 
sents the  external  os  {orificium  externum  uteri).  The  mucosa  of  the 
cervical  canal  shows  a  large  number  of  oblique  folds,  the  plicce 


THE    PARAMETRIUM  333 

palmatcB,  while  the  mucosa  in  the- body  is  smooth.  The  mucosa  at 
the  external  os  is  usually  pouched  forming  the  ventral  and  dorsal 
lips  {labium  anterius  et  labium  posterius.  The  fundus,  the  ventral 
surface  of  the  cervix  and  the  entire  dorsal  surface  and  cervix  are 
invested  with  peritoneum. 

The  lateral  border  (margo  lateralis)  separates  the  two  surfaces  and 
here  the  broad  ligament  is  attached. 

The  uterus  is  supported  by  a  number  of  ligaments.  The  two  broad 
ligaments  (ligamenta  lata  uteri)  extend  from  the  side  of  the  uterus 
to  the  lateral  pelvic  wall  and  are  covered  by  the  peritoneum.  From 
the  free  edge  of  each  extends  the  mesosalpinx.  Each  round  liga- 
ment {ligamentum  teres  uteri)  extends  from  the  junction  of  the  oviduct 
and  the  fundus,  under  the  peritoneum,  to  the  internal  abdominal 
ring;  from  here  it  passes  through  the  inguinal  canal  and  is  lost  in 
the  tissues  of  the  labium  majus.  The  two  ventral,  or  uterovesical 
ligaments,  extend  from  the  uterus  to  the  bladder.  The  two  dorsal 
ligaments,  or  rectovaginal  folds,  extends  from  the  uterus  and  vagina 
to  the  rectum.  The  uterorectal  folds  {plica  rectouterine?)  extend  from 
the  uterus  to  the  rectum  and  contain  the  utcrosacral  ligaments. 

The  position  of  the  uterus  varies  with  the  position  of  the  body  and 
the  condition  of  the  neighboring  organs.  In  a  ventral  view  it  is 
seen  bent  usually  toward  the  right  side;  in  the  erect  position,  when 
the  bladder  is  empty,  the  uterus  usually  rests  upon  the  bladder  and 
is  then  bent  forward  and  downward  on  the  cervix  so  that  the  axis 
of  the  organ  is  not  a  straight  line.  This  is  called  anteflexion.  If  the 
uterus  as  a  whole  is  tilted  forward  it  constitutes  anleversion;  as  the 
bladder  fills  the  uterus  becomes  more  erect.  When  the  bladder  is 
full  and  the  rectum  empty  the  organ  may  be  bent  backward  and  be 
either  retroverted,  or  retroflexed. 

The  parametrium  is  that  rather  thick  layer  of  loose  tissue  between 
the  two  layers  of  peritoneum  of  the  broad  ligament,  below  the  level  of 
the  mesosalpinx.  Where  the  broad  ligament  joins  the  pelvic  dia- 
phragm will  be  found  the  ureter  and  the  uterine  vessels.  Below 
these  vessels  the  fibrous  and  muscle  tissue  form  the  lateral  cervical 
ligament,  on  each  side. 

In  the  female  at  birth  the  cervical  portion  of  the  uterus  predomi- 
nates and  the  plica;  extend  through  the  cavity.  The  organ  grows 
slowly  until  just  before  puberty  when  it  rapidly  increases  in  size  and 
the  plica;  in  the  body  disappear.  In  old  age  the  uterus  becomes 
harder  and  paler. 

During  the  child-bearing  period  the  uterus  undergoes  periodic 
changes,  called  menstrual  changes.  The  menstrual  flow  recurs  every 
twenty-eight  days. 

The  arteries  of  the  uterus  are  the  uterine  and  ovarian  arteries,  the 
branches  of  which  form  an  extensive  anastomosis. 


334 


THE  FEMALE  ORGAN'S  OF  REPRODUCTION 


The  veins  form  a  plexus  that  empties  into  the  tributaries  of  the 
internal  iliac  veins. 

The  nerves  are  derived  from  the  uterovaginal  plexus  connected 
with  the  hypogastric  and  vesical  plexuses  of  the  sympathetic  system 
and  branches  are  received  from  the  third  and  fourth  sacral  nerves. 
THE  VAGINA 

The  vagina  is  a  flattened,  musculomembranous  tube  that  connects 
the  external  genitalia  with  the  uterus.  Its  ventral  and  dorsal  walls 
are  in  contact  and  the  cavity  is  a  transverse  or  H-shaped  slit  that 
extends  ventrodorsally.  The  ventral  wall  is  about  3  inches  (7.5  cm.) 
in  length,  while  the  dorsal  wall  is  about  3J-2  inches  (8.75  cm.)  long. 


Fig.   245. — Medi; 


:ittal  section  of  the  female  pelvis. 


The  cervix  projects  into  the  vagina  and  as  a  result  the  vaginal  cavity 
projects  around  the  end  of  the  cervix,  constituting  the  ventral  and 
dorsal  fomices,  respectively;  at  the  sides  of  the  cervix  are  the  lateral 
forn ices.     In  the  ventral  wall  lies  the  urethra. 

The  arteries  are  derived  from  the  uterine,  vaginal  branches  of 
the  hypogastric  (internal  iliac)  and  branches  from  the  internal  puden- 
dal and  middle  hemorrhoidal  arteries.  The  veins  form  a  dense 
plexus  and  empty  into  the  hypogastric  veins.  The  nerves  are 
derived  from  the  uterovaginal  and  vesical  plexuses  of  the  sympa- 
thetic system  and  from  the  third  and  fourth  sacral  nerves. 
THE  EXTERNAL  GENITALIA 

The  external  genitalia  (pudendum  muliebre)  comprise  the  mans 
veneris,  the  labia  majora,  the  labia  minora,  the  vestibule,  elitoris, 
glands  of  Bartholin  and  the  hymen. 


THE    EXTERNAL    GENITALIA 


335 


The  mons  veneris  {commissura  labiorum  anterior)  is  the  pad  of 
fat  covered  with  skin  and  hairs  over  the  symphysis  pubis. 

The  labia  majora  are  two  linear  folds  of  skin  extend- 
ing from  the  mons  veneris  toward  the  anus.  In  the  midline  they  lie 
in  contact  and  this  line  of  contact  constitutes  the  pudendal  slit  (rima 
pudendi).  The  adjacent  surfaces  of  the  labia  are  covered  by  mucous 
membrane.  Just  in  front  of  the  anal  region  the  folds  are  quite  low 
and  are  connected  by  a  transverse  - 
fold  called  the  posterior  commissure 
{commissura  labiorum  posterior). 

When  the  labia  majora  are 
separated  two  smaller  folds,  the 
labia  minora  are  exposed.  At 
their  pubic  extremities  they  are 
united  and  surround  the  clitoris, 
forming  its  prepuce  (preputium 
clitoridis)  and  frenulum  {frenulum 
clitoridis);  anally  they  diverge 
and  fuse  with  labia  majora. 
Near  this  region  a  transverse  fold, 
the  fourchette  {frenulum  labiorum 
pudendi)  connects  the  labia  minora 
and  forms  the  posterior  boundary 
of  the  vaginal  orifice.  The  de- 
pression between  the  fourchette 
and  dorsal  commissure  is  the  fossa 
navicular  is.  The  long  triangular 
area  between  the  labia  minora  is 
the  vestibule  {vest ibul urn  vagina). 
Here  are  seen  the  vaginal  and 
urethral  orifices  and  the  opening 
of  the  ducts  of  the  vestibular 
glands. 

The    vaginal    Orifice     {orificium     G.  hymen;  If .  fourchette 

vagina)  is  the  larger  and  occupies 

the  dorsal  part  of  the  vestibule  or  basal  part  of  the  triangle.  Between 
the  orifice  of  the  vagina  and  the  converged  labia  minora  (pubically) 
is  a  triangular  area  near  the  middle  of  which  is  seen  the  urethral 
orifice  {orijicum  urethra:  externum).  Upon  each  side  of  the  vaginal 
orifice,  beneath  the  mucous  membrane  and  extending  to  the  clitoris 
region,  is  a  bulb-like  mass  of  erectile  tissue,  the  bulbus  vestibuli. 

The  hymen  is  a  variable  fold  of  tissue  which  tends  to  cover  the 
vaginal  orifice.     It  is  usually  crescentic  in  shape  but  may  be  absent. 

The  glands   of  Bartholin   {gland  ul  a:  vestibularis   ma  fores)    are   in 
relation  with  the  triangular  ligament  and  their  ducts  empty  into  the 


Fig.  246. — External  organs  of  reproduc- 
tion of  the  female.  A,  Anterior  commis- 
sure; B.  clitoris;  C,  labium  minus;  P.  ves- 
tibule; E,  urethral  orifice;  F,  vaginal  orifice; 


336 


THE  FEMALE  ORGANS  OF  REPRODUCTION 


space  between  the  vaginal  orifice  and  the  labia  minora.  Each  is 
elongated  and  about  the  size  of  a  bean.  They  represent  the  glands 
of  Covvper  of  the  male. 

The  clitoris  is  the  analog  of  the  penis  minus  a  corpus  spongiosum. 
It  arises  by  two  crura  from  the  sides  of  the  pubic  arch  and  these  con- 
tinue as  the  corpora  cavernosa  clitoridis  that  meet  and  form  the  body 
of  the  clitoris  (corpus  clitoridis);  this  is  connected  to  the  symphysis 


Fig.    247. — Female  perineum  dissected.      .-1.  Clitoris;  B,  crus  of  the  clitoris;  C,  bulb  of  the 
vestibule;  D,  urethral  orifice;  E.  vagina. 

by  a  suspensory  ligament  (ligament  siispensorium  clitoridis).  At 
the  end  of  the  body  is  a  small  rounded  mass  of  erectile  tissue  the 
glans  clitoridis,  that  is  very  sensitive.  The  glans  is  covered  by,  the 
prepuce  (preputium  clitoridis)  derived  from  the  labia  minora.  The 
body  of  the  clitoris  is  about  ijjj  inches  (3  cm.)  long. 

Arteries — The  artery  of  the  clitoris  is  the  deep  artery  of  the  clit- 
oris from  the  internal  pudendal.  Its  nerves  are  derived  from  the 
hypogastric  plexus  of  the  sympathetic  system  and  the  internal  pudic 
nerve.  The  glans  is  supplied  by  the  dorsal  artery  of  the  clitoris.  The 
bulbits  vestibuli  is  supplied  by  the  artery  of  the  bulb  from  the  internal 
pudendal  artery.  The  nerves  are  from  the  hypogastric  plexus  and 
branches  from  the  pudendal  nerves. 

THE  MAMMARY  GLANDS 

The  mammary  glands  (mamma)  although  not  directly  connected 
with  the  reproductive  organs  are  best  considered  here  as  they  are 
accessories.  Each  is  a  hemispherical  mass  in  the  superficial  fascial  of 
the  upper,  ventral  thoracic  wall,  extending,  usually,  from  the  second 


THE    MAMMARY    GLAND 


337 


to  the  sixth  rib.  Each  is  surmounted  by  a  nipple  (papilla  mamma) 
which  is  of  variable  size  and  shape;  it  is  usually  in  the  lower,  outer 
quadrant  of  the  gland.  The  nipple  is  darker  in  color  than  the  gland 
proper  and  is  surrounded  by  a  circular  area  of  darkened  skin.  This 
area  is  the  areola.  The  amount  of  pigment  in  the  areola  and  nipple 
varies.  On  the  summit  of  the  nipple  are  seen  small  depressions  into 
which  the  milk  ducts  empty.  During  lactation  the  organ  consists 
mainly  of  glandular  tissue  and  is  firmer  and  larger  than  in  the  non- 


mary  gland  through  the  nipple 


lactating  period.  During  this  latter  period  the  glandular  tissue  is 
reduced  to  a  minimum  and  the  organ  consists  chiefly  of  adipose  and 
white  fibrous  tissues  and  gland  ducts.  In  early  childhood  there  is 
very  little  or  no  difference  between  the  mammae  of  the  male  and 
female.  Toward  the  age  of  puberty,  in  the  female,  the  mamma; 
begin  to  grow  rapidly. 

The  arteries  of  the  mammary  gland  are  the  internal  mammary 
artery  and  branches  from  the  lateral  thoracic  and  intercostal  arteries. 
The  veins  empty  the  blood  into  the  internal  mammary  and  axillary 
veins.  The  nerves  are  from  the  thoracic  sympathetics  and  from  the 
fourth,  fifth  and  sixth  intercostal  nerves. 


CHAPTER  XI 


THE  DUCTLESS  GLANDS 


The  ductless  glands  comprise  the  spleen,  thymus,  thyreoid,  para- 
thyreoids,  adrenals,  carotid  bodies,  coccygeal  body,  parasympathetic 
bodies,  pituitary  and  pineal  bodies. 

THE  THYREOID  BODY 

The  thvreoid  bodv,  or  gland  is  located  in  the  neck  at  the  sides  of 
the  larynx  and  over  the  upper  part  of  the  trachea.  It  weighs  about 
25  grams  and  measures  2  inches  (5  cm.)  in  width  and  2.4  inches  (6 
cm.)  in  height.  It  consists  of  tuo 
lateral  lobes  and  a  middle  lobe,  or 
isthmus.  This  is  not  always  the  case 
as  it  may  be  horseshoe-shaped,  or 
have  the  form  of  a  notched  sphere,  or 
may  be  in  two  distinct  parts.  Each 
lateral  lobe  is  somewhat  conical  in 
shape,  its  apex  resting  upon  the  side 
of  the  ala  of  the  thyreoid  cartilage 
and  the  base  extending  down  to  the 
fifth  or  sixth  tracheal  ring.  The 
isthmus  is  a  narrow  band  of  gland- 
ular tissue  that  connects  the  two 
lateral  lobes  across  the  second,  third 
and  fourth  of  the  trachea  rings. 
Occasionally  a  pyramidal  lobe  (said 
to  occur  in  40  per  cent.)  is  seen 
extending  upward  from  the  upper 
margin  of  the  isthmus.  Being  firmly  attached  to  the  underlying 
structures  the  thyreoid  follows  the   larynx   in   its  movements. 

The  arteries  are  the  superior  and  inferior  thyreoid  arteries.  The 
superior  and  middle  thyreoid  veins  emptv  into  the  internal  jugular 
vein  of  each  side;  the  inferior  thyreoid  vein  joins  its  fellow  of  the 
opposite  side  to  empty  into  the  left  innominate  vein. 

The  nerves  are  derived  from  the  middle  and  inferior  cervical 
ganglia  of  the  sympathetic  system. 

THE  PARATHYREOIDS 

The  parathyreoids  are  usually  four  in  number,  two  superior  and 
iuv  inferior,  although  as  many  as  twelve  may  be  present.     Each 
338 


Fig.    249. — Thy 


oid    gland,     ventral 
1  a  photograph.) 


THE    CHROMAPHYL    SYSTEM 


339 


weighs  from  o.oi  gram  to  3  grams  and  is  about  J4  inch  (6  mm.)  in 
length  and  about  %  inch  [3  mm.)  in  diameter.  They  are  yellowish 
brown  in  color  and  may  be  lenticular,  or  nearly  spherical  in  shape. 
The  superior  are  behind  the  lateral  lobes  of  the  thyreoid  body  at  the 
level  of  the  lower  border  of  the  cricoid  cartilage.  The  inferior  are 
variable  in  position  and  may  be  found  behind 
the  lower  part  of  the  lateral  lobes  and  at  a 
distance  below.  Each  is  supplied  by  a  branch 
from  the  inferior  thyreoid  artery. 

CHROMAPHYL  SYSTEM 

A  number  of  small  organs  in  the  body  stain 
peculiarly  when  treated  with  chromium  salts; 
they  secrete  adrenalin  and  are  classed  under 
the  chromaphyl  system.  The  adrenals  are  the 
largest  and  the  others  comprise  the  carotid 
bodies,  aortic  bodies  and  paraganglia;  all  are 
closely  associated  with  the  sympathetic 
system. 

THE  ADRENALS 

The  adrenals,  or  suprarenal  glands  {glandula- 
suprarcnales)  are  two  in  number.  Each  is  of 
a  yellowish  color  externally,  and  darkish 
brown  (chromaphvl  tissue)  internally.    Each 

lies  in  the  epigast'ric  region  and  is  in  relation    ^^"^  inf^ 
with  the  upper  part   of   the    kidney.     Each    parathyroids,  respectively, 
organ  weighs  about  6  to  7  grams  and  meas- 
ures 2  inches  (5  cm.)  in  height,  i'2  inches  (3.75  cm.)  in  width  and 
about  '-4  to  *2  inch  (6  to  12  mm.)  in  thickness. 

The  right  adrenal  is  triangular  in  outline  and  its  base  rests 
upon  the  superior  extremity  of  the  right  kidney.  Upon  its 
ventral  surface  is  seen  a  furrow,  the  hilus,  at  which  the  supra- 
renal vein  emerges. 

The  left  adrenal  is  semilunar  in  shape  and  its  base  rests  upon  the 
upper  part  of  the  medial  border  and  a  part  of  the  superior  extremity 
of  the  kidney.     Upon  its  ventral  surface  is  seen  the  hilus. 

The  adrenals  are  retroperitoneal. 

The  arteries  are  the  suprarenal  arteries  from  the  aorta,  and 
branches  from  the  renal  and  inferior  phrenic  arteries.  The  right 
suprarenal  vein  empties  into  the  inferior  vena  cava  while  the  left 
empties  into  the  left  renal  vein. 

The  nerves  are  derived  from  the  suprarenal  plexus  and  branches 
from  the  solar  and  renal  plexuses  of  the  sympathetic  system  and  from 
the  greater  splanchnic,  vagal  and  phrenic  nerves. 


Fig.  250. — Dorsal  view  of 
the  parathyreoids    and   the 


.HO 


THE    DUCTLESS    GLANDS 
CAROTID  BODIES 


The  intercarotid  bodies  (glomus  caroticum)  are  two  small  bodies 
structures  situated  at  the  bifurcation  of  each  common  carotid  artery. 
Each  is  about  the  size  of  a  grain  of  wheat  (3  mm.  by  1  mm.).  Each 
is  closely  connected  with  the  carotid  sympathetics  and  is  grayish- 
reddish  brown,  or  yellowish  in  color. 


Rig  h  1~Jlclrena.  / 


Fig.  2si.— The  adrenals,  ventral  view.     (From  a  fholograph.) 

COCCYGEAL  GLAND 

The  coccygeal  gland  is  located  in  front  of  the  tip  of  the  coccyx  and 
is  smaller  than  the  preceding  gland.  It  is  in  close  relation  with  the 
middle  sacral  artery. 

PARASYMPATHETIC  BODIES 

The  parasympathetic  bodies  (aortic  bodies)  are  two  to  three  in  num- 
ber and  are  seen  in  the  fetus  and  in  early  childhood.  They  are  retro- 
peritoneal and  are  found  in  front  of  the  aorta  in  the  neighborhood 
of  the  third  and  fourth  lumbar  vertebra;  at  the  origin  of  the  inferior 
mesenteric  artery.  Their  blood  supply  is  from  the  aorta.  Each  is 
brownish  in  color,  about  8  to  11  mm.  long  and  3  mm.  in  diameter. 

The  pituitary  body,  or  hypophysis  and  the  pineal  body,  or  epiphysis 
will  be  described  under  the  "Nerve  System."  The  spleen  and  thy- 
mus have  already  been  described  under  the  "Lymphatic  System." 


CHAPTER  XII 
THE  EYEBALL  AND  LACRIMAL  APPARATUS 

The  eyeball  and  part  of  the  lacrimal  apparatus  lie  in  each  orbital 
fossa. 

The  orbital  fossae  are  pyramidal  cavities  on  each  side  of  the  bridge 
of  the  nose  and  below  the  frontal  bone,  in  the  upper  part  of  the  face 
region.  Each  is  about  2  inches  (5  cm.)  deep.  The  base,  or  orbital 
aperture  is  forward  on  the  face  while  the  apex  is  directed  backward 
and  medially  and  is  represented  by  the  optic  foramen.  It  has  a  roof, 
floor,  and  two  walls,  a  lateral  and  a  medial.  The  bones  that  form  the 
boundaries  of  each  fossa  are  the  frontal,  lacrimal,  ethmoid,  sphenoid, 
malar,  maxilla  and  palate  bones.  At  the  front  of  the  orbit  at  the 
junction  of  the  floor  and  medial  wall  is  seen  a  groove,  the  lacrimal 
fossa  (fossa  sacci  lacrimalis)  and  an  opening  extending  into  a  bony 
canal.  The  fossa  and  opening  lodge  the  lacrimal  sac,  while  the  bony 
canal  is  for  the  nasal  duct.  At  the  upper  and  inner  portion  of  the 
front  of  the  orbit  is  a  spine,  or  a  depression  (spina  vel  fovea  trocfdearis) 
for  the  attachment  of  the  pulley  of  the  superior  oblique  muscle.  In 
the  temporal  portion  of  the  orbit  is  a  depression  wherein  is  lodged 
the  lacrimal  gland. 

Within  the  orbit  is  lodged  the  eyeball,  the  muscles  that  operate 
it,  the  capsule  of  Tenon  and  the  orbital  fat,  vessels  and  nerves. 

The  capsule  of  Tenon  (fascia  bulbi)  is  a  lymph  space  of  bursa 
wherein  the  eyeball  moves  as  free  from  friction  as  possible.  This  is 
a  double  layer  of  serous  membrane  that  covers  the  posterior  portion 
of  the  eyeball  and  extends  as  far  forward  as  the  reflection  of  the  con- 
junctiva. The  layers  are  practically  in  apposition.  It  is  pierced 
posteriorly  by  the  optic  nerve  and  continues  thereon.  It  is  likewise 
pierced  further  forward  by  the  tendons  of  the  ocular  muscles  and 
prolonged  upon  each  in  the  form  of  a  tubular  sheath.  That  portion 
of  the  fascia  under  the  eyeball  is  formed  like  a  sling,  or  hammock  and 
seems  to  support  the  eyeball  and  has,  therefore,  been  called  the  s«s- 
peusory  ligament. 

The  extrinsic  muscles  are  the  rectus  superior,  rectus  inferior,  rectus 
lateralis,  rectus  medialis,  obliquus  superior  and  obliquus  inferior. 
The  four  recti  muscles  arise  from  a  tendinous  ring  around  the  optic 
foramen,  the  lateralis  having  two  heads.  These  muscles  pass  for- 
ward and  are  inserted  into  the  sclera  at  about  8  mm.  from  the  cor- 
neoscleral junction.  The  superior  and  inferior  recti  are  inserted 
into  the  vertical  plane  a  little  medial  to  the  axis  of  the  eyeball  while 
341 


342 


THE    EYEBALL    AND    LACRIMAL    APPARATUS 


the  lateral  and  medial  recti  are  inserted  in  the  horizontal  plane.  The 
superior  oblique,  a  digastric  muscle,  arises  a  little  above  and  medial 
to  the  ring  and  passes  forward  to  the  upper  and  inner  angle  of  the 
orbit  to  pass  through  the  pulley  and  then  turns  outward  between  the 
superior  rectus  and  the  eyeball  to  be  inserted  into  the  sclera  between 
the  superior  and  lateral  recti  muscle  midway  between  the  cornea  and 
optic  nerve  area,  behind  the  equator  of  the  eyeball. 

The  inferior  oblique  arises  at  the  front  of  the  orbit  just  lateral  to 
the  lacrimal  fossa.  It  passes  outward  between  the  eyeball  and  the 
floor  of  the  orbit,  then  upward  between  the  lateral  rectus  and  the 
eyeball  to  be  inserted  into  the  sclera  between  the  lateral  and  superior 
recti  muscles,  a  little  further  back  than  the  superior  oblique. 


252. — Muscles  of  the  right  orbit. 


The  lateral  and  medial  recti  muscles  move  the  eyeball  horizontally 
outward  and  inward.  The  superior  rectus  moves  the  eyeball  ver- 
tically upward  when  assisted  by  the  inferior  oblique,  while  the  in- 
ferior rectus  moves  the  eyeball  vertically  downward  when  assisted 
by  the  superior  oblique.  The  inferior  oblique  rotates  the  eyeball 
laterally,  while  the  superior  oblique  rotates  the  eyeball  medially. 

The  orbital  fat,  usually  considerable,  serves  as  a  cushion  for  the 
eyeball.  It  varies  in  quantity  in  different  individuals  and  in  health 
and  sickness.  It  fills  in  the  orbital  fossa  around  the  eyeball  and  is 
most  abundant  behind  that  organ. 


THE  EYEBALL 


The  eyeball  {bulbus  oculi)  occupies  the  anterior  portion  of  the  orbit 
being  protected  by  the  orbital  margins  and  the  eyelids.  The  antero- 
posterior and  the  transverse  diameters  are  24  mm.  while  the  vertical 
diameter  is  23.5  mm.  so  that  the  eyeball  is  not  quite  a  sphere  at  the 
equator.     At  birth  the  eyeball  is  about  17.5  mm.  in  diameter  and  is 


THE    CORNEA 


343 


nearly  spherical  in  shape.     It  increases  about  3  mm.  between  birth 
and  puberty  and  soon  thereafter  attains  its  adult  size  and  shape. 

The  apparent  difference  in  the  size  of  the  eyeballs  of  different 
individuals  is  not  due  to  a  real  difference  in  size  but  to  a  difference 
in  the  prominence  of  the  eyeball  and  width  of  the  palpebral  fissure. 
When  viewed  from  the  side  the  eyeball  is  seen  to  consist  of  parts  of 
two  spheres.  The  smaller,  anterior,  corneal  portion  (about  one- 
sixth)  represents  part  of  a  sphere  of  14  mm.  diameter,  while  the 
larger,  posterior  portion  (five-sixths),  represents  the  greater  part  of 


a  sphere  of  24  mm.  diameter.  The  optic  axis  is  represented  by  a 
line  connecting  the  anterior  and  posterior  poles,  that  is  the  central 
points  of  anterior  and  posterior  curvatures,  respectively.  The 
equator  is  the  line  around  the  eyeball  midway  between  the  poles. 
The  visual  axis  is  a  line  that  passes  from  the  first  nodal  point  of  the 
cornea  to  the  fovea  centralis  of  the  retina. 

The  eyeball  is  called  the  organ  of  vision  {organon  visits).  In 
reality  it  makes  an  image  like  a  camera,  while  nerve  impulses  that 
are  generated  by  the  cells  of  the  retina  travel  to  the  brain  and  these 
impulses  are  then  translated  into  photic  impressions. 

The  eyeball  consists  of  three  coats,  or  tunics:  (1)  the  corneoscleral 
(tunica  fibrosa  ocitli);  (2)  the  choroid,  ciliary  body  and  iris,  or  the 
uveal  tract;  (3)  the  retina. 

1.  The  cornea  constitutes  about  one-sixth  of  the  circumference  of 
the  eyeball  and  is  transparent.     It  represents  one  of  the  important 


344  THE    EYEBALL    AND    LACRIMAL    APPARATUS 

refractive  media  of  the  eyeball.  It  is  composed  mainly  of  white 
fibrous  tissue  arranged  in  layers,  covered  externally  by  epithelium 
and  internally  by  endothelium.  It  is  thinner  in  the  axial  region 
(0.9  mm.)  and  at  the  corneoscleral  region  is  about  1.2  mm.  thick. 
The  curvature  is  greater  in  youth  than  in  old  age. 

The  sclera,  or  white  of  the  eyeball  consists  of  about  five-sixths  of 
the  circumference  and  is  composed  of  dense  white  fibrous  tissue. 
It  is  the  protective  coat  and  serves  for  the  attachment  of  the  ocular 
muscles.  That  portion  of  the  sclera  where  the  optic  nerve  passes  out 
is  sieve-like  and  is  called  the  lamina  cribrosa.  Between  the  sclera 
and  the  capsule  of  Tenon  is  the  episcleral  lymph  space.  Between 
the  sclera  and  the  choroid  is  the  sitbsclcral  lymph  space.  Besides 
being  pierced  by  the  optic  nerve  fila  it  is  perforated  by  the  posterior 
ciliary  arteries  and  the  vena;  vorticosas.  It  is  thinnest  at  the 
equator. 

2.  The  uveal  tract,  consisting  of  choroid,  ciliary  body  and  iris,  is 
also  called  the  vascular  coat  (tunica  vasculosa  oculi). 

The  choroid  (chorioidea)  is  the  most  extensive  of  the  three  divi- 
sions. It  lies  between  the  sclera,  externally,  and  the  retina,  inter- 
nally and  extends  forward  to  the  ora  serrata.  It  is  a  loose  coat  and 
contains  the  large  blood-vessel  trunks  of  the  eyeball,  in  its  outer 
part,  and  a  capillary  plexus  near  its  inner  border.  The  pigment 
layer  of  the  retina  adheres  firmly  to  it.  Between  it  and  the  sclera 
is  a  meshwork  (lamina  suprachorioidea)  covered  with  endothelium, 
constituting  the  suprachoroidal,  or  subscleral  lymph  space.  It  is  the 
posterolateral  part  of  the  choroid  coat  that  gives  the  peculiar 
metallic  reflex  of  the  lower  animals. 

The  ciliary  body  (corpus  ciliarc)  comprises  the  ciliary  ring,  ciliary 
muscle  and  the  ciliary  processes.  The  ciliary  ring  is  indicated  upon 
the  outside  of  the  eyeball  by  a  4-mm.  area  encircling  the  eyeball  at 
the  edge  of  the  cornea.  It  is  mainly  fibrous  tissue  supporting  the 
blood-vessels  of  that  region. 

The  ciliary  processes  (processes  ciliarcs)  are  sixty  to  seventy  radially 
placed  ridges  that  start  at  the  end  of  the  choroid  and  extend  to  the 
base  of  the  iris  where  they  end  abruptly  at  about  1  mm.  in  height, 
They  vary  in  length  from  2  to  5  mm.  and  they  are  not  all  of  the  same 
height.  They  contain  blood-vessels  and  are  covered  by  the  pig- 
mented layer  of  the  retina  (pars  ciliaris  retincc). 

The  ciliary  muscle  (m.  ciliaris)  consists  of  smooth  muscle  and  is 
arranged  chiefly  in  two  sets,  radial  and  circular.  The  radial  fibers 
arise  at  the  corneoscleral  junction,  radiate  backward  to  be  attached 
to  the  processes  and  ciliary  ring.  They  constitute  the  tensor  chor- 
ioidea; muscle.  These  fibers  are  usually  the  more  numerous.  The 
cirt  ular  fibers  lie  under  the  radial  fibers  near  the  base  of  the  iris. 
These  muscles  are  part  of  the  intrinsic  muscles  of  the  eyeball. 


THE    RETINA  345 

The  iris  is  the  automatic  curtain  of  the  eyeball  regulating  the 
amount  of  light  that  enters  the  organ.  In  its  center  is  the  pupillary 
aperture  which  varies  in  size  under  varying  amounts  of  light.  The 
iris  consists  mainly  of  white  fibrous  tissue,  covered  anteriorly  by 
endothelium  and  posteriorly  by  the  pigmented  layer  of  the  retina 
(pars  iridica  retina).  It  contains  two  sets  of  smooth  muscle,  one, 
the  circular  fibers,  arranged  circularly  near  the  pupillary  aperture. 
This  is  called  the  sphincter  pupilla  muscle,  for  by  contraction  it 
diminishes  the  pupillary  aperture.  The  second  set  or  radial  fibers 
extend  outward  from  the  circular  fibers  to  the  base  of  the  iris  and 
constitute  the  dilatator  papilla  muscle,  for  by  contraction  they  in- 
crease the  size  of  the  pupillary  aperture.  In  the  center  of  the  iris 
are  found  also  the  blood-vessels  (to  be  described  later)  and  varying 
quantities  of  pigmented  connective-tissue  cells  that  give  the  color 
to  the  eyeball. 

The  retina  is  the  neural,  or  image-making  coat  of  the  eyeball,  i.e., 
concerned  with  the  formation  of  an  image.  It  is  usually  called  the 
expanded  portion  of  the  optic  nerve  but  it  is  more  than  that  and 
very  complex  in  structure.  It  consists  of  two  main  parts,  the  pig- 
mented layer  and  the  true  neural  portion  (consisting  of  nine  complete 
layers).  The  pigmented  layer  is  composed  of  pigmented  columnar 
epithelial  cells  that  are  firmly  attached  to  the  glassy  membrane  of 
the  choroid  and  continue  over  the  ciliary  region  and  iris  as  pars 
ciliaris  and  pars  iridica  retina,  respectively.  The  neural  portion- 
extends  only  to  the  end  of  the  choroid  where  it  ends  in  a  serrated 
edge,  the  ora  serrata.  This  part  of  the  retina  constitutes  the  pars 
optica  retina.  .  Its  cellular  elements  are  the  layer  of  rods  and  cones, 
the  outer  and  inner  ganglionic  layers.  The  layer  of  nerve  fibers 
ultimately  forms  the  optic  nerve.  The  important  regions  of  the 
retina  are  the  blind  spot,  yellow  spot  and  the  ora  serrata. 

The  blind  spot  (optic  disc)  is  so-called  because  no  image  can  be 
formed  there.  It  is  whitish  in  color.  It  represents  the  area  of 
convergence  of  nerve  fibers  that  constitute  the  optic  nerve.  It  is 
situated  about  3  mm.  to  the  nasal  side  and  about  2  mm.  below  the 
posterior  pole  of  the  eyeball.  It  is  about  1.5  mm.  in  diameter  and  is 
usually  slightly  depressed  in  the  center,  the  excavatio  papilla  nervi 
optici. 

The  macula  lutea,  or  yellow  spot  is  oval  in  shape  and  2  by  3  mm. 
in  its  diameters  and  lies  in  the  visual  axis.  Its  central  part  is  slightly- 
depressed  and  is  called  the  fovea  centralis. 

The  ora  serrata  is  the  region  at  which  the  pars  optica  retinae 
ends.  Here  the  retina  is  about  0.1  mm.  thick  while  at  the  optic 
nerve  region  it  is  about  0.4  mm.  in  thickness. 

In  the  eyeball  are  the  crystalline  lens,  aqueous  and  vitreous  humors, 
the  anterior,  posterior  and  vitreous  chambers. 


346        THE  EYEBALL  AND  LACRIMAL  APPARATUS 

The  crystalline  lens  (lefts  crystal!  iua)  is  a  transparent,  biconvex 
lens  in  which  the  posterior  curvature  is  greater  than  the  anterior. 
The  posterior  curvature,  however,  is  practically  fixed  while  the 
anterior  curvature  is  variable.  It  lies  just  behind  and  in  contact 
with  the  iris  (at  the  pupillary  region)  and  rests  in  a  depression  in  the 
vitreous  humor  called  the  patellar  fossa  (fossa  patellaris).  It  is  about 
4  mm.  in  thickness  and  9  to  10  mm.  in  its  transverse  diameter.  It 
is  surrounded  by  a  capsule  the  anterior  layer  of  which,  at  the  edge  or 
equator  of  the  lens,  is  continuous  with  the  anterior  layer  of  the  zonule 
of  Zinn.  This  zonule  represents  a  thick  and  plicated  portion  of  the 
hyaloid  membrane  of  the  vitreous  humor  that  is  moulded  around  the 
ciliary  processes  and  intervening  depressions.  This  anterior  layer  is 
called  the  suspensory  ligament  of  the  lens.  The  bulk  of  the  lens  con- 
sists of  lens  fibers.  The  lens  represents  the  most  important  refract- 
ive medium  of  the  eyeball. 

The  vitreous  humor  (corpus  vitreum)  is  the  largest  structure  of 
the  eyeball  and  occupies  the  vitreous  chamber,  or  optic  cup,  that  repre- 
sents the  posterior  four-fifths  of  the  eyeball.  The  jelly-like  sub- 
stance is  surrounded  by  the  hyaloid  membrane  (membrana  hyaloidea). 
On  the  anterior  surface  is  the  patellar  fossa  for  the  posterior  surface 
of  the  lens.  At  the  ora  serrata  region  the  hyaloid  membrane 
becomes  thickened  and  strengthened  by  radial  fibers  and  this  con- 
stitutes the  zonule  of  Zinn  (zonula  ciliaris).  As  the  zonule  advances 
over  the  ciliary  processes  toward  the  lens,  it  is  moulded  over  and 
attached  to  the  processes  and  invaginated  into  but  not  attached  to 
the  depressions.  As  the  equator  of  the  lens  is  approached,  the  zonule 
splits  into  two  layers,  the  anterior  and  thicker  blending  mainly  with 
the  anterior  layer  of  the  lens  capsule  and  sending  fibers  to  the 
posterior  layer  (that  lines  the  patellar  fossa).  The  vitreous  humor 
represents  one  of  the  refractive  media  but  is  usually  disregarded  in 
ophthalmology. 

The  aqueous  humor  is  merely  lymph  that  occupies  the  anterior 
and  posterior  chambers. 

The  anterior  chamber  [camera  oculi  anterior)  is  the  space  between 
the  back  of  the  cornea  and  the  front  of  the  iris  and  is  filled  with 
aqueous  humor.  The  angle  formed  at  the  junction  of  iris  and  cornea 
is  the  infiltration  angle. 

The  posterior  chamber  (camera  oculi  posterior)  is  the  space 
between  the  back  of  the  iris  and  the  front  of  the  lens  and  suspensory 
ligament.  It  is  filled  with  aqueous  humor  and  communicates  with 
the  anterior  chamber  through  the  pupillary  aperture. 

The  optic  nerve  (nervits  opticus)  is  1 '  L.  to  2  inches  (3.75  to  5  cm.) 
in  length,  from  the  eyeball  to  the  chiasm.  It  begins  as  the  nerve- 
fiber  layer  of  the  retina,  mainly,  but  also  contains  fibers  that  have  a 
centrifugal  course.  It  traverses  the  orbital  fat  and  leaves  the  orbit 
through  the  optic  foramen. 


THE    EYELID    AND    CONJUNCTIVA  347 

The  blood-vessels  of  the  eyeball  are  the  central  retinal  artery 
(arteria  centralis  retina:)  the  short  and  long  posterior  ciliary  arteries 
and  the  anterior  ciliary  arteries.  The  central  retinal  artery  enters  the 
optic  nerve  near  the  eyeball  and  passes  into  the  eyeball  to  supply  the 
retina.  Its  blood  is  returned  by  the  central  vein  that  has  a  cor- 
responding course. 

The  short  posterior  ciliary  arteries,  about  six  to  twelve  in  number, 
pierce  the  sclera  near  the  optic  nerve  region  to  enter  the  choroid.  In 
the  choroid  they  form  the  layer  of  large  vessels  and  then  the  choroidal 
capillaries  and  these  branches  anastomose  with  those  of  the  other 
arteries.     They  supply  a  part  of  the  sclera. 

The  long  posterior  ciliary  arteries,  two  in  number,  pierce  the  sclera 
at  some  distance  from  the  optic  nerve  and  pass  between  the  sclera 
and  choroid  to  the  ciliary  muscle  where  they  form  the  cir cuius 
arteriosus  major,  at  the  base  of  the  iris,  by  anastomosis.  From  this 
circle  vessels  pass  to  the  pupillary  margin  to  form  the  cir  cuius  arte- 
riosus minor. 

The  anterior  ciliary  arteries,  four  in  number,  form  a  plexus  at  the 
edge  of  the  cornea.  Branches  pierce  the  sclera  and  connect  with  the 
circulus  iridicus  major. 

The  blood  from  the  long  and  short  ciliary  arteries  is  carried  to  the 
veno?  vorticosa  and  then  to  the  ophthalmic  vein.  Most  of  the  blood 
from  the  anterior  ciliary  arteries  is  returned  by  the  anterior  ciliary 
veins. 

The  lymphatic  spaces  of  the  eyeball  are  intercommunicating.  The 
anterior  chamber  communicates  with  the  posterior  and  with  the 
spaces  in  the  sclera  and  cornea  and  with  the  venous  canal  of  Schlemm, 
by  means  of  the  spaces  of  Fontana.  The  posterior  chamber  com- 
municates with  the  spaces  in  the  choroid  and  retina  and  through 
these  with  the  subarachnoidean  space  around  the  optic  nerve.  The 
capsule  of  Tenon  receives  lymph  from  the  subscleral  space  and  from 
the  choroid  by  means  of  the  vessels  around  the  venae  vorticosae  and 
the  lymph  is  then  transmitted  to  the  subarachnoidean  space  around 
the  optic  nerve. 

The  nerves  comprise  the  long  and  short  ciliary  nerves  and  ciliary 
ganglion. 

THE  EYELIDS  AND  CONJUNCTIVA 

The  eyelids  (palpebral)  are  two  transverse  folds  of  skin,  attached 
to  the  upper  and  lower  orbital  regions,  that  protect  the  eyeball. 
The  cleft  between  the  two  eyelids  is  called  the  palpebral  fissure  and 
measures  about  30  mm.  though  this  varies  in  the  different  races. 
The  outer  surface  is  covered  with  skin  while  the  inner  surface  is  a 
mucous  membrane  called  the  conjunctiva.  Between  these  two  layers 
are  fibrous  and  muscle  tissues  and  the  tarsal  plate  containing  the 
tarsal  glands.     At  the  margin  are  seen  two  rows  of  heavy  hairs  the 


348  THE    EYEBALL    AND    LACRIMAL    APPARATUS 

eyelashes,  or  cilia.  The  medial  and  lateral  angles  at  which  the  lids 
meet  are  called  the  medial  and  lateral  canthi,  or  commissures,  respect- 
ively. Near  the  medial  canthus  of  each  lid  is  a  minute  elevation, 
the  papilla  lacrimalis;  the  minute  orifice,  or  punctum,  found  therein  is 
the  beginning  of  the  lacrimal  duct  system.  Medial  to  the  papilla  is 
seen  the  caruncida  lacrimalis. 

The  conjunctiva  (tunica  conjunctiva  palpebro?)  is  a  mucous  mem- 
brane that  lines  the  inner  surface  of  each  lid  and  is  reflected  onto  the 
sclera  of  the  eyeball  {tunica  conjunctiva  bulbi)  just  in  front  of  the 
insertion  of  the  ocular  muscles.  It  continues  to  the  edge  of  the 
cornea  where  its  epithelium  only  passes  onto  that  part  of  the  eyeball. 
The  region  where  the  conjunctiva  is  reflected  from  the  lid  to  the 
sclera  is  called  the  fornix  conjunctiva;  (superior  and  inferior).  When 
the  lids  are  in  apposition  the  conjunctiva  represents  a  closed  sac. 

THE  LACRIMAL  APPARATUS 

The  lacrimal  apparatus  comprises  the  lacrimal  glands,  the  puncta, 
canalicidi,  lacrimal  sacs  and  nasal  ducts. 


Fig.  254. — The  lacrimal 'apparatus  of  the  right 


The  lacrimal  glands  (glandulm  lacrimales)  one  in  each  orbital 
fossa,  is  located  in  the  upper  and  lateral  (temporal)  part  of  the  orbit 
in  the  lacrimal  fossa.  It  is  flattened  and  the  main  portion  measures 
about  12  by  20  mm.  The  ducts,  three  to  nine  in  number,  empty  into 
the  conjunctival  sac  between  the  upper  edge  of  the  eyelid  and  the 
fornix. 

The  punctum,  one  in  each  eyelid,  is  located  near  the  inner  canthus 
upon  the  summit  of  a  little  papilla.  It  leads  into  a  canaliculus.  The 
canaliculus  (ductus  lacrimalis)  one  in  each  eyelid,  of  which  that  in 


THE    NASAL    DUCT  349 

the  upper  eyelid  is  the  shorter,  connects  each  punctum  with  the 
lacrimal  sac. 

The  lacrimal  sac  (sacus  lacrimalis)  represents  the  dilated  upper 
extremity  of  the  nasal  duct.  It  is  about  12  to  15  mm.  long,  4  to  5 
mm.  wide  and  7  mm.  thick.  It  lies  in  the  lacrimal  groove  and  re- 
ceives the  canaliculi. 

The  nasal  duct  (ductus  nasolacrimalis)  is  about  18  mm.  long  and 
3  to  4  mm.  in  diameter.  It  passes  inward  and  backward  and  opens 
into  the  inferior  meatus  of  the  nasal  cavity  under  cover  of  the  inferior 
conchal  bone. 


CHAPTER  XIII 

THE  EAR  (ORGANON  AUDITUS) 

The  car,  or  auditory  apparatus  consists  of  three  parts  the  external, 
middle,  or  tympanum  and  internal  or  labyrinth  portions. 

THE  EXTERNAL  EAR 

The  external  portion  comprises  the  pinna  and  external  auditory 
canal.  The  pinna,  or  auricle,  is  a  peculiarly  moulded  mass  of  elastic 
cartilage  covered  with  skin  and  adapted  to  catch  the  sound  waves 
and  conduct  them  into  the  external  auditory  canal.  It  is  of  an  oval 
form  and  is  located  midway  between  the  forehead  and  the  occiput. 
It  is  attached  to  the  side  of  the  head  and  its  cartilage  continues  as  a 
tube  that  forms  a  part  of  the  external  auditory  canal.  Its  parts 
are  the  helix  and  antihelix,  the  tragus  and  antitragus  and  the  lobule. 
The  latter  contains  no  cartilage  and  is  very  vascular.  The  muscles 
of  the  pinna  are  intrinsic  and  extrinsic.  The  extrinsic  muscles  are 
the  atlrahens  aurem  {m.  auricularis  anterior)  which  is  the  smallest 
and  is  in  front;  the  atolens  aurem  (m.  auricularis  superior)  which  is 
the  largest  and  is  above;  the  retrahens  aurem  [m.  auricularis  poste- 
rior) which  is  behind  the  pinna.  These  muscles  are  of  very  little 
importance  in  man.  The  intrinsic  muscles  are  the  mm.  helicis  major, 
helicis  minor,  tragicus,  antitragicus  and  the  transversus  and  obliquus 
auricular  (B. 

The  external  auditory  canal  [canal is  auditorius  extcrnus)  is  about 
i  inch  (2.5  cm.)  in  length  when  measured,  as  it  should  be,  from  the 
bottom  of  the  concha.  It  is  like  an  elongated  S  in  shape  and  its 
general  direction  is  forward  and  inward.  It  makes  an  angle  of  about 
45°  with  the  sagittal  plane  and  its  diameter  varies  in  the  different 
parts.  Its  anterior  and  inferior  walls  are  longer  than  the  posterior 
and  superior  walls  on  account  of  the  slope  of  the  tympanic  membrane. 
The  lateral  one-third  is  called  the  cartilaginous  portion  (pars  carti- 
laginea)  and  is  formed  by  the  tube-like  continuation  of  the  pinna; 
the  medial  two-thirds  is  called  the  osseous  portion  (pars  ossea)  because 
its  walls  are  formed  by  bone  (temporal).  This  canal  is  lined  by  skin 
continued  from  the  pinna  and  in  it  are  found  the  ceruminous,  or 
wax  glands  (glandulce  ceruminosa)  and  many  hairs  (barbula  hirci). 

THE  MIDDLE  EAR 

The  middle  portion,  or  tympanum  (cavum  tympani)  consists  of  the 
tympanic  cavity  proper,  the  attic,  the  membraua  tympani,  the  ossicles 
and  its  connection  with  the  pharynx,  the  auditory  tube. 
35° 


THE    TYMPANIC    CAVITY 


351 


The  tympanic  cavity  proper,  or  atrium  lies  just  medial  to 
the  tympanic  membrane  and  is  a  narrow  space,  quadrilateral  in 
shape.  It  is  placed  practically  parallel  to  the  sagittal  plane  of  the 
body.  Its  length  and  height  are  15  mm.  each.  The  distance 
between  the  lateral  and  medial  walls  varies;  at  the  top  it  is  6  mm.,  in 
the  middle  about  2  mm.  and  at  the  bottom  about  4  mm.  Above  the 
level  of  the  tympanic  membrane  the  tympanic  cavity  forms  a  recess 
called  the  attic  (recessus  epitympanicus) ,  or  epitympanum.  This 
recess  contains  most  of  the  incus  and  half  of  the  handle  of  the  mal- 
leus and  communicates  with  the  mastoid  antrum.     In  the  anterior 


Fig.  255. — Vertical  section  through  the  external  auditory  canal  and  tympanum.  At 
Epitympanic  recess;  B.  tympanum;  C,  fenestra  oralis  closed  by  foot  of  the  stapes;  Mem.. 
tympanic  membrane. 

wall  {paries  carotica)  of  this  cavity  are  two  openings;  the  upper 
represents  the  orifice  of  the  canal  that  transmits  the  tensor  tympani 
muscle  (semicanalis  m.  tenso'ris  tympani)  while  the  lower  represents 
the  orifice  of  the  auditory  tube.  The  medial  wall  \ paries  labyrinthica) 
has  an  oval  opening,  the  fenestra  vestibuli;  its  long  axis,  3  mm.,  is 
directed  horizontally  while  its  shorter  axis  is  directed  vertically  and 
measures  about  1.5  mm.  In  the  recent  slate  this  orjening  is  closed 
by  the  foot  of  the  stapes  held  in  position  by  the  annular  ligament 
{ligamentum  annulare).  In  the  dried  bone  this  opening  leads  into 
the  vestibule  of  the  internal  portion  of  the  ear.  Below  the  fenestra 
vestibuli  is  another  opening  (in  the  dried  bone)  that  leads  into  the 
cochlea  and  is  termed  the  fenestra  cochlea.  In  the  recent  state  it  is 
closed  by  the  membrana  tympani  secundaria. 


352 


THE    EAR 


The  tympanic  antrum  {antrum  tympanicum)  is  a  cavity  in  the 
temporal  bone  that  is  about  8  by  10  mm.  and  connects  the  epitym- 
panum  with  the  mastoid  cells.  The  mastoid  cells  (cellules  mastoidece) 
vary  in  number  and  size  and  are  said  not  to  be  developed  until  the 
sixth  year.     In  the  adult  they  are  usually  quite  numerous. 

The  tympanic  membrane  (membra na  tympani)  is  an  elliptical, 
disc-shaped  membrane  that  slopes  downward,  medially  and  back- 
ward, thus  accounting  for  the  difference  in  the  length  of  the  walls  of 
the  external  auditory  canal.  It  is  about  10  mm.  in  its  vertical 
dimension  and  9  mm.  from  side  to  side.  Its  circumference  is  thick- 
ened by  circularly  directed  fibers  of  the  annidus  fibrocartilagineus , 
that  attaches  it  to  the  circumference  of  the  medial  end  of  the  external 
auditory  canal.  Above  the  malleolar  prominence  (formed  by  the 
handle  of  the  malleus)  is  the  pars  flaccida.  The  bulk  of  the  mem- 
brane is  tense,  constituting  the  pars  tensa.  The  central  part  of  the 
membrane  is  drawn  slightly  inward  by  the  attached  handle  of  the 
malleus  and  is  called  the  umbo. 

The  lateral  surface  of  the  membrane  is  covered  by  a  thin  skin 
and  the  medial  surface  by  a  delicate  mucous  membrane.  The  cir- 
cular and  radial  fibers  between  these  two  layers  are  .thinner  in  the 
middle  than  at  the  circumference. 

The  muscles  of  the  middle  ear  are  the  m.  tensor  tympani  and  the 
m.  stapedius.  The  insertion  of  the  tensor  tympani  upon  the  medial 
edge  of  the  anterior  surface  of  the  handle  of  the  malleus  is  such  that 
when  the  muscle  contracts  the  handle  is  drawn  medially  and  the 
membrane  is  rendered  tense.  The  stapedius  is  inserted  into  the 
neck  of  the  stapes  and  by  its  contraction  the  anterior  end  of  the 
base  of  the  stapes  is  tilted  laterally  and  the  posterior  end  medially, 
thus,  probably,  compressing  the  lymph  in  the  vestibule. 

The  tympanic  ossicles  (ossicula  auditus)  or  ear  bones  (Fig.  255)  are 
three  in  number  upon  each  side.  These  are  the  malleus,  incus  and 
stapes. 

The  malleus  is  the  largest  having  a  length  of  8  to  9  mm.  It 
is  composed  of  head,  neck,  handle,  long  and  short  processes.  The 
head  (caput)  articulates  with  the  body  of  the  incus.  The  handle 
(manubrium)  is  directed  downward,  medially  and  backward  and  is 
attached  along  its  entire  length  to  the  tympanic  membrane. 

The  incus  consists  of  a  body  and  two  processes.  The  body  (corpus) 
has  a  facet  for  articulation  with  the  head  of  the  malleus.  The  long 
process  (crus  longum)  is  directed  almost  perpendicularly  downward 
and  at  its  low  extremity  it  articulates  with  the  head  of  the  stapes. 

The  stapes  consists  of  the  head,  neck,  two  crura  and  a  base.  The 
head  (caput)  articulates  with  the  long  process  of  the  incus.  The 
oval  base  (basis)  rests  in  the  fenestra  vestibuli  and  is  held  in  position 
by  the  ligamciitum  annulare. 


THE    INTERNAL    EAR  353 

The  auditory  tube  (tuba  auditiva)  connects  the  tympanic  cavity 
with  the  pharynx.  The  air  which  it  transmits  to  the  tympanic 
cavity  serves  to  maintain  an  equilibrium  of  pressure  upon  both  sides 
of  the  tvmpanic  membrane.  The  lateral  end  opens  upon  the 
anterior  wall  of  the  tympanic  cavity.  The  tube  is  about  i ]  2'  inches 
(36  mm.)  in  length  and  is  directed  downward  at  an  angle  of  about 
30°  to  40°  to  the  horizontal  plane  and  forward  and  medially  at  an 
angle  of  about  450  to  the  sagittal  plane.  It  opens  into  the  naso- 
pharvnx.  Its  lateral  one-third  is  the  osseous  portion  (pars  ossea) 
and  the  medial  two-thirds  the  cartilaginous  portion  (pars  carlilaginea) . 
The  cartilage  is  in  the  form  of  a  T-shaped  hook  in  which  the  anterior 
wall  is  completed  by  fibrous  tissue.  The  cartilage  projects  into  the 
nasopharynx  (covered  by  mucosa)  constituting  the  eustachian 
cushion  (torus  tubarius).  Some  of  the  fibers  of  the  tensor  veli 
palatini  muscle  take  origin  from  the  upper  end  of  the  hook  and  have 
been  called  the  dilatator  tuba-  muscle. 

THE  INTERNAL  EAR 

The  internal  portion  of  the  ear,  or  labyrinth  is  the  most  important 
portion  of  the- auditory  apparatus.  It  is  located  in  the  petrous 
portion  of  the  temporal  bone  and  comprises  the  osseous  and  mem- 
branous labyrinths . 

The  bony  labyrinth  (labyrinthus  osseus)  consists  of  the  vestibule, 
the  semicircular  canals  and  the  cochlea. 

The  vestibule  (vcstibulum)  lies  between  the  semicircular  canals, 
behind,  and  the  cochlea,  in  front.  It  is  about  6  mm.  anteroposte- 
riorly  and  4  to  5  mm.  from  above  downward  and  3  mm.  from  without 
inward.  In  its  lateral  wall  is  seen  the  fenestra  vestibuli  closed  by  the 
base  of  the  stapes  and  its  ligament.  It  lodges  the  sacculus  (recessus 
sphcricus)  and  the  itlricnlus  (recessus  cllipticus)  and  numerous 
foramina  that  transmit  nerve  fibers  from  the  sacculus  and  utriculus 
and  lower  end  of  the  cochlear  duct,  are  noted  here. 

The  semicircular  canals  (canales  semicircular es  ossei)  are  behind  and 
above  the  vestibule.  They  are  three  in  number  in  each  ear 
and  are  called  superior,  lateral  and  posterior.  Each  forms  about  two- 
thirds  of  a  circle  and  is  about  1  to  1.5  mm.  in  diameter.  One 
extremity  of  each  is  dilated  and  this  is  the  ampulla  which  is  2  mm. 
in  diameter.  These  canals  communicate  with  the  vestibule  by 
five  openings.  The  superior  canal  is  vertical  and  is  placed  trans- 
versely to  the  long  axis  of  the  petrous  portion  of  the  temporal  bone. 
Its  length  is  about  18  mm.  The  lateral  canal  is  placed  almost  hori- 
zontally and  measures  12  to  15  mm.  in  length.  The  posterior  canal 
is  about  20  mm.  in  length.  The  opposite  lateral  canals  lie  in  the 
same  plane  while  the  superior  canal  of  one  ear  is  parallel  to  the  poste- 
rior canal  of  the  other  ear. 


354  THE  EAR 

The  cochlea  represents  a  tapering  tube,  of  28  to  30  mm.  length, 
spirally  wound  for  nearly  234  turns  about  a  bony  axis,  the  modiolus. 
The  broad  portion  is  the  base  that  measures  about  9  mm.  across  and 
is  in  relation  with  inferior  fossula  of  the  internal  auditory  meatus. 
The  end  of  the  coil  is  the  apex,  or  cupola;  it  is  about  5  mm.  above 
the  base  and  about  2  mm.  above  the  apex  of  the  modiolus.  The 
basal  portion  of  the  tube  is  about  2  mm.  in  diameter. 

The  modiolus,  or  axis  is  a  conical  mass  about  3  mm.  high  and  is 
pierced  by  many  foramina  for  the  transmission  of  nerve  fibers. 
Upon  the  tube  side  the  modiolus  sends  out  a  bony  shelf  that  extends 


Fig.   256. — Isolated  membranous  labyrinth  of  the 


A,  ductus  endolymphaticus. 


about  halfway  across  the  tube  and  is  called  the  lamina  spiralis 
(ossea).  The  division  of  the  tube  is  completed  by  the  basilar 
membrane  that  extends  from  the  spiral  lamina  to  the  lateral  wall  of 
the  osseous  tube.  As  a  result  two  passage-ways  are  formed,  the 
upper  the  scala  veslibuli  and  the  lower  the  scala  iympani.  At  the 
modiolus  end  of  the  spiral  lamina  is  a  canal  that  extends  the  length 
of  the  shelf  and  in  this  spiral  canal  is  lodged  the  spiral  ganglion  of 
Corti  {ganglion  spirale).  The  spiral  lamina  and  basilar  membrane 
extends  to  within  a  short  distance  of  the  end  of  the  tube  and  here 
the  two  scalae  communicate  with  each  other.  This  communication 
is  called  the  helicotrema. 

Within  the  bony  labyrinth  is  a  membranous  cast  called  the  mem- 
branous labyrinth  (labyrinlhicus  membranaceous).  This  cast  is 
separated  from  the  bony  walls  by  the  perilymph.  Within  the  mem- 
branous labyrinth  is  the  endolymph.  The  parts  are  the  sacculus, 
utriculus,  the  semicircular  canals  and  the  cochlear  duct. 

The  sacculus  and  utriculus  lie  in  the  osseous  vestibule.  The  saccu- 
lus lies  in  the  lower  and  front  part,  is  oval  in  shape  and  measures 


THE    MEMBRANOUS    LABYRINTH 


355 


2  by  3  mm.  It  is  smaller  than  the  utriculus.  It  presents  a  thick- 
ened neuroepithelial  area,  the  macula  acuslica  sacculi.  The  saccule 
communicates  with  the  cochlear  duct  by  means  of  a  small  canal,  the 
ductus  reuniens.  Another  canal,  the  ductus  endolymphaticus ,  passes 
through  the  aqueductus  vestibuli  to  end  in  a  small  sac  under  the 
dura,  in  the  cranial  cavity.  This  duct  is  met  by  a  canal  from  the 
utriculus,  the  ductus  utriculosaccular  is,  thereby  giving  an  indirect 
communication  between  these  two  structures. 

The  utriculus  lies  in  the  posterior  and  superior  part  of  the  bony 
vestibule.  It  is  larger  than  the  preceding  and  its  highest  part  com- 
municates with  the  ampullae  of  the  superior  and  lateral  membranous 


semicircular  canals.  The  lower  medial  part  communicates  with  the 
ampulla  of  the  posterior  canal.  The  central  part  communicates  with 
the  lateral  canal  and  above  this  with  the  common  opening  of  the 
posterior  and  superior  canals.  The  utriculus  possesses  a  whitish, 
neuroepithelial  area,  the  macula  acustica  utriculi.  From  the  utriculus 
the  ductus  utriculosaccularis  passes  to  the  ductus  endolymphaticus. 

The  membranous  semicircular  canals  (ducti  circulates)  represent 
casts  of  the  osseous  canals,  but  are  only  one-fourth  the  diameter 
of  the  latter.  In  the  ampullae  are  found  neuroepithelial  areas,  the 
crista  acustica.  The  semicircular  canals  seem  to  be  the  organs  of 
equilibrium,  the  canals  being  arranged,  apparently,  in  the  three 
dimensions  of  space. 

The   membranous   cochlea    (ductus   cochlcaris)    cochlear   duct,   or 


356  THE    EAR 

scala  media  is  a  limited  portion  of  the  scala  vestibuli.  From  the 
spiral  lamina  the  thin  membrane  of  Reissner  {membrana  vestibularis) 
passes  upward  and  laterally  at  an  angle  of  about  450  to  be  attached 
to  the  lateral  wall  of  the  scala  vestibuli.  This  forms  a  tube,  triangu- 
lar in  section,  the  scala  media,  or  cochlear  duct,  which  is  closed  at  its 
apical  end,  constituting  the  lagena.  The  basal  end  of  the  cochlear 
duct  lies  in  the  vestibule  and  communicates  by  means  of  the  ductus 
reuniens  with  the  saccule.  Upon  the  medial  end  of  the  basilar  mem- 
brane is  the  important  part  of  the  auditory  apparatus,  the  organ  of 
Corti  (organum  spirale).  This  consists  of  supporting  and  neuroepi- 
thelial (hair)  cells  that  form  a  mass  that  has  a  spiral  course  upon  the 
basilar  membrane  and  extends  the  length  of  the  scala  media.  The 
hair  cells  are  about  15,000  in  number  and  constitute  the  neuroepithe- 
lial elements  that  translate  the  lymph  waves  into  nerve  impulses. 
These  impulses  are  transmitted  to  the  brain  and  there  translated  into 
auditory  impressions. 

The  blood  supply  of  the  pinna  and  external  auditory  canal  is  from 
the  posterior  auricular  and  superficial  temporal  arteries,  chiefly; 
the  veins  from  the  former  empty  into  corresponding  veins  while  the 
veins  from  the  latter  empty  into  the  external  jugular  and  external 
maxillary  veins. 

The  nerves  of  the  pinna  are  the  auriculotemporal,  the  small 
occipital  and  the  great  auricular.  Those  of  the  external  canal  are 
the  auriculotemporal  and  auricular  branch  of  the  vagus. 

The  blood  supply  of  the  tympanum  is  as  follows:  The  membrana 
tympani  is  supplied  laterally  by  the  deep  auricular  branch  of  the 
internal  maxillary  while  the  medial  side  receives  its  blood  from  the 
tympanic  branch  of  the  internal  maxillary  mainly.  The  veins 
laterally  empty  into  the  external  jugular  and  medially  into  the  plexus 
of  the  auditory  tube  or  into  the  lateral  sinus.  The  nerves  are  later- 
ally from  the  trigeminus  and  medially  from  the  glossopharyngeus. 

The  arteries  that  supply  the  tympanic  cavity  are  branches  of  the  pos- 
terior auricular,  internal  maxillary,  middle  meningeal,  internal  car- 
otid and  ascending  pharyngeal  arteries.  The  veins  empty  into  the 
superior  petrosal  sinus,  the  pterygoid  plexus  and  the  middle  menin- 
geal vein.  The  nerves  are  from  the  pharyngeal  plexus.  The  tensor 
tympani  muscle  is  supplied  by  the  trigeminus  (through  the  otic  gang- 
lion) and  the  stapedius  by  the  facial  nerve. 

The  blood  supply  of  the  labyrinth  is  the  auditory  artery  from  the 
basilar  artery.  This  gives  rise  to  three  branches,  the  anterior  ves- 
tibular, the  cochlear  and  the  vestibulocochlear  arteries.  The  audi- 
tory veins  return  the  blood  to  the  inferior  petrosal  sinus,  or  to  the 
lateral  sinus. 

The  nerve  of  the  labyrinth  is  t  he  auditory  nerve.  This  consists 
of  two  portions,  vestibular  and  cochlear.     The  vestibular  division  con- 


THE  NERVES  OF  THE  LABYRINTH  357 

sists  of  three  portions,  one  from  the  utriculus,  one  each  from  the 
ampullae  of  the  superior  and  lateral  semicircular  canals.  The  coch- 
lear division  consists  of  three  parts,  one  from  the  sacculus,  one  from 
the  posterior  semicircular  canal  and  the  third,  the  bulk  of  this  divi- 
sion, from  the  organ  of  Corti. 


CHAPTER  XIV 


THE  NERVE  SYSTEM 


The  nerve  system  (systema  nervorum)  is  the  most  important  and 

most  complicated  apparatus  in  the  body.     It  serves,  through  various 

sensations  and  impressions,  to  make  us  cognizant  of  our  surroundings 

and  give  us  the  power  to  adapt  ourselves  to  our  environments.     It 

presides  over  motion  and  sensation 

and  the  functions  of   the  various 

organs  are  subjected  to  its  control. 

It  is  most    highly    developed    in 

man  and  consists  of  two  kinds  of 

nerve  tissue,  gray  and  white. 

It  is  composed  of  units  called 
neurons  that  are  linked  together 
in  such  a  manner  so  as  to  give 
direct  and  indirect  connections 
between  the  central  system  and 
the  periphery  of  the  body.  Each 
neuron  consists  of  a  cell  and  its 
processes. 

Gray  nerve  tissue  is  composed 
of  nerve  cells,  their  processes,  nerve 
fibers  a.nd  a  distinctive  supportive 
tissue,  the  neuroglia.  A  neuron  is 
a  nerve  cell  and  its  processes.  The 
cell  body,  or  cytom,  comprises  a 
mass  of  protoplasm  varying  from 
4M  to  1 20M  in  diameter  and  exhibits 
a  granular  and  fibrilar  structure. 
The  basophilic  granules  are  large 
but  inconstant  depending  upon 
the  state  of  the  cell.  These 
granules  are  called  the  corpuscles 
of  Nissl,  or  tigroid  bodies.  Their 
position,  size  and  number  depends 
upon  the  functional  activity  of  the 
cell;  they  may  be  diffusely  scattered  and  small,  or  arranged  in  groups 
around  the  nucleus,  or  near  the  periphery  and  extend  into  the  minor 
processes,  or  dendrites.  In  fatigued  cells  they  disintegrate  and  dis- 
appear. The  fibrillar  character  is  due  to  the  neurofibrils  that  extend 
throughout  the  protoplasm  forming  an  apparent  network  but  the 
358 


TdereuntB 

Fig.  258.— Nerve  cells.     A,  Multipolar;  B. 
bipolar;  C.  diagram  of  a  neuron. 


NERVE    FIBERS  359 

fibrils  do  not  really  form  junctions  with  one  another.  These  fib- 
rils pass  into  all  of  the  processes  and  form  the  most  important  part 
thereof.  They  are  brought  out  by  intravitam,  or  silver  nitrate  staining. 

The  nucleus  is  usually  large,  spherical  and  pale  in  appearance  as  it 
contains  but  little  chromatin.  It  is  usually  eccentrically  placed. 
The  nucleolus  is  large  and  stains  darkly. 

If  but  one  process  is  present  it  is  the  axone,  the  other  processes, 
when  present,  being  called  dendrites.  The  axone  is  the  main  process 
and  consists  of  a  number  of  neurofibrils  embedded  in  neuroplasm 
and  surrounded  by  a  delicate  sheath  called  the  axilemma.  This  proc- 
ess may  go  but  a  short  distance  in  the  gray  substance  and  terminate 
in  a  brush-like  manner  near  the  processes  of  another  cell  (second  type 
cell).  When  the  axone  leaves  the  gray  substance  and  becomes  sur- 
rounded by  a  myelin  sheath  and  a  neurilemma  it  constitutes  a  mye- 
linated fiber  and  the  cell  is  called  a  Dieter's  cell,  or  cell  of  the  first  type. 

The  dendrites  are  the  minor  processes  and  consist  mainly  of  neuro- 
fibrils that  extend  but  a  short  distance  from  the  cell  before  they 
branch  and  form  a  large  number  of  twigs  that  terminate  in  a  brush- 
like manner  near  the  processes  of  another  cell.  These  are  the  telo- 
dendrites  and  these  processes  serve  an  associative  function.  Some 
dendrites  are  quite  long,  leave  the  gray  substance  and  become  in- 
vested with  a  myelin  sheath  and  a  neurilemma  and  serve  as  a  nerve 
fiber. 

The  cells  that  possess  but  one  process,  as  those  of  the  ganglia  of 
the  dorsal  roots  of  the  spinal  nerves  and  certain  of  the  cerebral 
nerves,  are  called  unipolar.  When  two  processes  are  present,  as  in 
the  cochlear  and  vestibular  ganglia  and  the  Purkinje  cells  of  the 
cerebellum,  they  are  called  bipolar  cells.  When  more  than  two 
processes  are  present,  they  are  called  multipolar  cells,  as  are  seen  in 
the  cerebral  cortex  and  the  ventral  horns  of  the  spinal  cord  espe- 
cially.    The  latter  are  the  largest  cells  of  the  nerve  system. 

The  neuroglia  is  the  special  supportive  tissue  of  the  nerve  system 
and  comprises  glial  cells  and  glial  fibers.  The  cells  are  chiefly  stel- 
late, possessing  many  processes  that  may  be  short  and  thick,  or  long 
and  slender.  The  fibers  form  a  meshwork  that  supports  the  func- 
tionating nerve  cells. 

Nerve  fibers  may  be  myelinated,  as  seen  in  the  cerebrospinal  sys- 
tem, or  amyelinated,  as  seen  in  the  sympathetic  system.  A  myelin- 
ated nerve  fiber,  on  cross-section,  is  seen  to  consist  of  a  central  axis, 
the  axis-cylinder,  or  axons;  this  consists  of  neurofibrils  embedded  in 
neuroplasm  and  surrounded  by  an  axilemma.  This  is  surrounded  by 
the  myelin  sheath  that  is  composed  of  a  framework  of  neurokeratin 
containing  the  myelin  substance  [phosphorized  fat)  in  its  meshwork. 
It  is  apparently  an  insulating  sheath  and  is  surrounded  by  the 
neurilemma,  a  delicate  connective-tissue  sheath.     Upon  longitudinal 


360  THE    NERVE    SYSTEM 

section  a  nerve  fiber  shows  constrictions  (nodes  of  Ranvier)  at  regular 
intervals;  here  the  myelin  substance  is  wanting  and  the  neurilemma 
dips  in  and  touches  the  axilemma.  Here  only  may  collaterals  arise. 
Nerve  fibers  vary  from  2^  to  20ju  in  diameter. 

A  nerve  consists  of  a  number  of  nerve  fibers  in  one  mass  of 
variable  size.  The  number  of  nerve  fibers  varies  from  a  few  to 
450,000  to  800,000,  as  in  the  optic  nerve.  The  nerve  is  surrounded 
by  a  connective-tissue  sheath  called  the  epinemium.  This  sends  in 
septa  that  divides  the  nerve  into  large  secondary  bundles  and  these 
septa  send  in  others  that  form  sheaths  for  the  primary  bundles,  or 
fasciculi.  These  latter  sheaths  are  the  perineural  sheaths.  Fibers 
of  the  perineurium  pass  into  the  bundles  and  form  a  mesh  work,  the 
endoneurium,  that  supports  the  nerve  fibers,  blood-vessels  and 
nerves  of  the  nerve. 

Nerve  fibers  are  sensor  and  motor  and  an  entire  nerve  as  the  hypo- 
glossal, accessory,  oculomotor,  trochlearis  and  abducens  may  be 
composed  entirely  of  motor  fibers  and  each  is  then  called  a  motor 
nerve.  A  nerve  may  be  composed  entirely  of  sensor  fibers,  as  the 
acoustic,  olfactory  and  optic  nerves  and  are  then  called  sensor. 
Some  nerves,  mixed,  have  both  sensor  and  motor  fibers  as  the  spinal, 
vagal,  glossopharyngeal,  trigeminal  and  facial  nerves.  Each  main 
division  of  such  a  nerve  is  distinguished  as  the  motor  root  and  the 
sensor  root. 

Although  there  are  two  divisions,  the  cerebrospinal  and  the  sym- 
pathetic, they  are  not  isolated  from  each  other,  but  are  intimately 
connected  by  intercommunicating  fibers,  the  rami  communicantes. 

The  cerebrospinal  system  comprises  the  centra!  portion,  i.e.,  brain, 
spinal  cord  and  their  meninges,  and  a  peripheral  portion,  the  cerebral 
and  spinal  nerves  and  their  ganglia. 

The  central  nerve  system  is  surrounded  and  protected  by  the 
bones  of  the  skull  and  the  vertebral  column.  The  cranial  part  fits 
rather  snugly  into  the  cranium  and  the  bones  surrounding  it  are 
immovable,  thus  affording  greater  protection.  The  spinal  portion 
is  situated  in  the  jointed  vertebral  column  but  the  vertebral  canal 
is  of  sufficient  diameter  to  admit  of  all  normal  movements  without 
injuring  the  spinal  cord.  The  central  nerve  system  is  not  solid  but 
possesses  a  central  cavity  system  throughout,  the  cavity  varying  in 
the  different  parts.  This  canal  system  is  a  characteristic  of  the 
nerve  system  of  the  vertebrates  only.  It  comprises  the  ventricles 
and  spinal  canal  and  contains  the  cerebrospinal  fluid.  It  communi- 
cates at  several  points  with  the  subarachnoid  lymph  spaces  around 
the  central  system  and  by  means  of  these  communications  the  intra- 
neural and  the  extraneural  pressure  are  balanced.  Interference  with 
these  openings,  as  in  certain  diseases,  causes  a  disturbance  of  the 
balance  with  certain  attendant  symptoms. 


THE    MENINGES 


361 


The  meninges  comprise  three  membranes  the  dura,  arachnoid  and 
the  pia.  The  dura  {dura  mater)  is  a  thick  and  tough  white  fibrous 
tissue  membrane.  In  the  cranial  cavity  it  is  attached  to  the  bones 
and  acts  as  the  inner  periosteum  thereof  as  well  as  a  protection  to 
the  brain.  It  also  forms  the  falx  cerebri  which  is  a  vertical,  sickle- 
shaped  membrane  that  separates  the  cerebral  hemispheres  from  each 
other  in  the  sagittal  plane.  The  dura  forms  the  walls  of  the  venous 
sinuses  and  the  tentorium  cerebelli.     The  latter  lies  above  the  cere- 


PlG.   -'Mj. — Dried  spt 


ie  falx  cerebri  and  the  tentorium  cerebelli.      (From  a 
photographs 


bellum,  serves  to  support  the  weight  of  the  occipital  portion  of  the 
cerebrum  and  joins  the  falx  cerebri  and  the  falx  cerebelli.  The  dura 
also  forms  a  sheath  about  the  cerebral  nerves  for  a  short  distance. 
The  falx  cerebelli  is  a  vertical  septum  of  dura  that  lies  between  the 
two  cerebellar  hemispheres.  The  diaphragma  sella  is  a  portion  of 
the  dura  that  stretches  over  the  top  of  the  sella  turcica  of  the  sphe- 
noid bone  and  thus  converts  that  depression  into  a  fossa  in  which  the 
hypophysis  is  situated.  The  diaphragm  is  pierced  by  a  small  open- 
ing through  which  the  stalk  of  the  hypophysis  passes. 

In  the  vertebral  canal  the  dura  does  not  serve  as  a  periosteum  but 
is  suspended  as  a  loose  bag  that  extends  from  the  foramen  magnum 
to  the  third  division  of  the  sacrum.     Within  this  bag  is  the  spinal 


362  THE    NERVE    SYSTEM 

cord.  Between  the  dura  and  the  arachnoid  is  a  lymph  space  called 
the  subdural  lymph  space. 

The  arachnoid  (arachnoidea)  is  a  delicate,  web-like  membrane 
that  lies  between  the  dura  and  pia,  and  though  closely  applied  to 
the  latter  does  not  follow  it  into  the  fissures  and  sulci  except  in  the 
case  of  the  longitudinal  and  lateral  cerebral  fissures.  Between  the 
arachnoid  and  the  pia  is  the  subarachnoid  lymph  space  (cavum  sub- 
arachnoideale)  which  does  not  communicate  with  the  subdural  space. 
The  arachnoid  forms  a  number  of  reddish  bodies  that  project  into 
the  venous  sinuses.  These  are  the  Pacchionian  bodies  {granulationes 
arachnoideales)  and  although  they  may  appear  to  lie  within  the  sinu- 
ses they  are  covered  by  a  thin  layer  of  the  dura.  In  certain  regions 
the  arachnoid  and  pia  are  separated  from  each  other  forming  spaces, 
the  cisterna  subarachnoidcales.  The  cisterna  cerebellomedularis  is  the 
largest  and  is  situated  between  the  cerebellum  and  the  roof  of  the 
oblongatal  portion  of  the  fourth  ventricle.  The  cisterna  pontis  is 
in  relation  with  the  pons.  The  cisterna  inter peduncularis  is  in  the 
interpeduncular  space.  The  cisterna  chiastnatis  is  an  extension  of 
the  preceding  in  front  of  the  optic  chiasm. 

The  pia  {pia  mater)  is  the  vascular  membrane  of  the  brain  and  spinal 
cord.  It  is  closely  applied  to  the  surface  of  these  and  enters  all  of 
the  fissures  and  sulci,  more  so  in  the  cerebrum  than  in  the  cerebellum. 
The  larger  vessels  project  into  the  subarachnoid  space  while  the 
smaller  ones  ramify  the  pia  and  then  pierce  the  nerve  tissue. 

THE  SPINAL  CORD 

The  spinal  cord  (medulla  spinalis)  is  that  portion  of  the  central 
nerve  system  located  in  the  vertebral  canal.  It  is  somewhat  cylin- 
drical in  shape  and  extends  from  the  margin  of  the  foramen  magnum 
to  the  lower  border  of  the  first  or  upper  border  of  the  second  lumbar 
vertebra.  In  the  male  it  measures  about  18  inches  (45  cm.)  and  in 
the  female  about  17  inches  (43  cm.).  Its  weight,  when  stripped,  is 
about  30  grams  and  with  the  nerve  roots  about  45  grams.  Two 
enlargements  are  present,  one  in  the  cervical  portion  and  the  other  in 
the  lumbar  portion  of  the  cord.  The  former  {intumescentia  cervi- 
calis)  is  at  its  maximum  at  the  sixth  cervical  vertebra  (12  to  14  mm.) 
and  the  latter  {intumescentia  lumbal  is)  reaches  its  maximum  at  the 
twelfth  thoracic  vertebra  (n  to  13  mm.).  This  increase  is  due  to  the 
added  cells  and  fibers  for  the  appendages.  These  enlargements  vary 
in  size  according  to  the  use  of  the  appendages;  in  man,  ourang  and 
gibbon  the  cervical  enlargement  is  the  larger.  In  the  kangaroo  and 
ostrich  the  lumbar  enlargement  is  the  larger.  In  animals  without 
appendages  these  enlargements  are  barely  perceptible. 

The  terminal  portion  of  the  spinal  cord  is  cone-shaped  and  is  called 
the  conus  medullaris.     This  includes  the  three  lower  sacral  and  the 


THE    SPINAL   CORD 


363 


coccygeal  segments.     Its   formation   is    due   to    the    reduction   in 
quantity  of  the  gray  and  white  substances. 

Extending  from  the  conus  is  a  thread,  the  filum  terminale,  that 


Fig.  260. — Dorsal  view  of  the 
spinal  cord  and  membranes  in  situ. 
The  vertebral  arches  have  been  re- 
moved.     {From  a  photograph.) 


Fig.  261. — Model  of  the  pons,  ob- 
longata and  spinal  cord  in  situ  (ventral 
view),  a.  Pons;  b,  cervical  enlarge- 
ment; c,  brachial  plexus,  d,  thoracic 
nerves  (ventral  divisions) ;  t,  lumbar 
enlargement  and  conus;  /,  Cauda 
equina;  g,  lumbosacral  plexus;  h* 
cervical  sympathetic  ganglia;*,  tho- 
racic sympathetic  ganglia ;  k,  I. 
splanchnic 


is  nearly  10  inches  (25  cm.)  in  length.  It  consists  chiefly  of  the  pia 
and  about  one-half  lies  within  the  dural  sac  and  its  remainder  exter- 
nal to  the  sac.  Its  peripheral  end  is  attached  to  the  coccyx.  In 
the  early  months  of  fetal  life,  the  spinal  cord  is  as  long  as  the  verte- 


364  THE    NERVE    SYSTEM 

bral  canal.  As  the  cord  grows  less  rapidly  than  does  the  vertebral 
column,  it  recedes  from  the  bottom  so  that  at  birth  it  extends  to  the 
lower  border  of  the  fourth  lumbar  vertebra  and  in  the  adult  to  the 
upper  border  of  the  second  lumbar  vertebra.  In  the  earliest  condi- 
tion the  nerves  pass  out  at  right  angles  to  the  cord  while  in  the  adult, 
in  order  to  continue  out  of  the  proper  foramen  of  exit,  each  of  the 
lower  nerves  lengthens  as  the  cord  recedes  and  forms  a  more  acute 
angle.  As  a  result  the  lower  end  of  the  cord  is  surrounded  by  bundles 
of  nerve  fibers  resembling,  thus,  a  horse's  tail;  this  constitutes  the 
cauda  equina. 

The  spinal  cord  presents  a  number  of  fissures  and  grooves.  Yen- 
trally  in  the  midline  is  the  ventromcdian  fissure  {Jissura  mcdiana 
anterior)  the  depth  of  which  is  about  one-third  the  dorsoventral 
diameter  of  the  cord.  Dorsally  in  the  midline  is  the  dorsomedian 
groove  {sulcus  mcdiana  posterior) .  Where  the  dorsal  roots  of  the  spinal 
nerves  enter  there  is  a  groove,  upon  each  side  of  the  cord  called  the 
dorsolateral  groove  {sulcus  lateralis  posterior) ;  midway  between  this  and 
the  dorsomedian  groove  lies  the  dorso paramedian  groove  {sulcus  inter- 
medins posterior)  upon  each  side  of  the  cord.  The  cord  is  divided 
into  halves,  longitudinally,  by  the  ventromedian  fissure  and  the 
dorsomedian  septum.  The  latter  extends  all  of  the  way  from  the 
surface  to  the  gray  commissure. 

Upon  transverse  section,  the  spinal  cord  is  seen  to  consist  of 
internal  gray  and  external  while  nerve  tissues. 

The  gray  substance  is  arranged  in  the  form  of  an  H-shaped  column, 
the  dorsoventral  bars  representing  the  horns,  or  cornua  and  the 
transverse  bar  the  gray  commissure  {commissure  grisea).  In  the  gray 
commissure  is  the  central  canal  {caualis  centralis).  That  portion 
of  each  horn  ventral  to  the  level  of  the  canal  is  the  ventral  horn 
{columua  anterior)  and  that  behind  is  the  dorsal  horn  {columna 
posterior).  The  ventral  horns  are  the  larger,  are  blunt  and  do  not 
extend  to  the  periphery  of  the  cord;  the  dorsal  horns  are  more  slender 
and  usually  extend  to  the  periphery  of  the  cord.  The  cornua  con- 
tain the  functionating  cells  of  the  spinal  cord. 

The  gray  nerve  tissue  consists  of  nerve  cells  their  processes,  neurog- 
lia and  nerve  fibers.  The  nerve  cells  are  arranged  in  groups  in  the 
ventral  horns  but  these  groups  vary  in  size  and  number  of  cells  in 
the  various  segments  of  the  cord.  The  ventral  horn  cells  are  the 
largest  nerve  cells  in  the  body.     The  various  groups  are  as  follows: 

1.  The  ventromedian  group  is  found  in  nearly  all  segments  of  the 
cord  (except  the  fifth  lumbar  and  the  first  sacral).  This  apparently 
represents  the  nuclei  of  origin  of  the  fibers  of  the  nerves  that  supply 
the  long  trunk  muscles. 

2.  The  dorsomedian  group  is  found  in  the  upper  cervical  segments, 
the  thoracic  and  first  lumbar  segments,  in  other  words  where  no  limb 
muscles  are  represented. 


THE    SPINAL    CORD  365 

3,  4.  The  ventrolateral  and  dorsolateral  groups  are  the  largest  and 
represent  the  nuclei  of  origin  of  the  nerves  to  the  muscles  of  the  limbs. 
These  groups  are  not  continuous  throughout  the  cord  but  are  found 
in  the  cervical  and  lumbar  enlargements  and  the  upper  sacral 
segments. 

5.  The  central  group  is  found  chiefly  in  the  lumbar  and  sacral 
segments. 

6.  The  intermediate,  or  lateral  group,  is  a  thin,  continuous  column  of 
cells  in  the  thoracic  and  first  two  lumbar  segments  with  recrudes- 
cences in  the  upper  cervical  and  third  and  fourth  sacral  segments. 
The  axones  from  these  cells  pass  to  the  sympathetic  ganglia  and 
represent  the  white  rami  rommunii  antes;  they  are  splanchnic  efferent 
fibers  representing  motor  connections  between  cerebrospinal  and 
sympathetic  systems. 

Although  many  axones  of  the  above  cells  form  the  nerve  fibers 
of  the  ventral  roots  of  the  spinal  nerves,  the  axones  of  the  other  cells 
have  a  different  course  and  function.  Some  of  these  axones  as  well 
as  myelinated  dendrites  pass  to  the  medial  and  lateral  sides  of  the 
ventral  horns  and  form  the  medial  and  lateral  ground  bundles. 
Upon  entering  these  bundles  the  fibers  branch  T-like  and  the  divi- 
sions pass  up  and  down  for  one  or  two,  and  occasionally  more, 
segments  and  then  turn  into  the  gray  substance  and  end  around  the 
cells  of  the  ventral  horns  of  those  segments.  These  fibers  represent 
intersegmental  association  fibers  and  serve  to  connect  several  seg- 
ments together  for  coordination  of  action  of  several  muscles,  or  mus- 
cle groups.  Other  cells,  especially  those  along  the  medial  side  of  the 
ventral  horns,  send  their  axones  and  dendrites  through  the  gray  com- 
missure to  the  other  side  of  the  cord  as  commissural  fibers.  The 
dendrites  pass  to  the  ventral  horn  cells  of  the  same  level  and  they  do 
not  leave  the  gray  substance.  The  axones  enter  the  white  substance 
of  the  ground  bundle  of  the  opposite  side,  branch  T-like  and  the 
ascending  and  descending  branches  ultimately  end  in  the  gray  a 
few  segments  above  and  below  to  terminate  around  the  cells  of  the 
ventral  horn. 

These  cells  ventral  to  the  intermediate  group  represent  somato- 
motor cells  while  those  of  the  intermediate  group  region  to  the  trans- 
verse line  through  the  canal  represent  the  visceromotor  cells. 

In  the  dorsal  horn  there  is  only  one  distinct  group  of  large  cells,  the 
other  cells  being  somewhat  scattered  and  small.  This  main-  group 
is  the  nucleus  of  Clarke  (nucleus  thoracis)  and  is  an  unbroken  column 
from  the  eighth  cervical  segment  to  the  second  lumbar  segment;  it 
lies  at  the  dorsal  side  of  the  cervix  of  the  dorsal  horn  (the  junction  of 
this  horn  with  the  gray  commissure).  Most  of  the  axones  of  these 
cells  pass  to  the  dorsolateral  columns  of  the  same  side  forming  the 
superficial  dorsolateral  spinocerebellar  tract.     The  other  axones  pass 


366  THE    NERVE    SYSTEM 

through  the  gray  commissure  to  the  opposite  side  (possibly  to  the 
white  substance)  constituting  axones  of  commissural  cells. 

The  other  cells  of  the  dorsal  horn  are  classified  as  marginal,  stellate 
and  spindle  cells.  The  marginal  cells  are  near  the  extremity  of  the 
dorsal  horn  and  the  axones  enter  the  lateral  columns  as  intersegmen- 
tal association  and  other  fibers.  The  stellate  cells  send  their  mye- 
linated dendrites  to  the  funiculus  cuneatus  of  the  dorsal  column. 
The  spindle  cells,  the  smallest,  send  their  axones  to  the  dorsal  col- 
umns. Some  of  these  cells  also  send  their  myelinated  axones 
through  the  dorsal  portion  of  the  gray  commissure  to  the  opposite 
side  to  form  there  the  two  spinothalamic  tracts,  the  spinotectal  and 
superficial  ventrolateral  spinocerebellar  tracts. 

These  cells  near  the  transverse  midline  of  the  dorsal  horns  repre- 
sent viscerosensor  cells  while  those  farther  dorsad  represent  somato- 
sensor  cells. 

The  neuroglia  consists  of  spider-like  cells  that  possess  a  small,  flat 
body  and  many,  long,  slender  processes.  In  addition  there  are  many 
glial  fibers  that  form  a  meshwork  for  the  support  of  the  nerve  cells 
and  vessels.  In  the  region  of  the  spinal  canal  there  is  an  especially 
dense  meshwork  of  these  fibers  called  the  substantia  grisea  centralis; 
around  the  peripheral  end  of  each  dorsal  horn  is  a  cap  of  neuroglia 
called  the  substantia  gelatinosa,  or  caput  cornualis.  This  contains  a 
few  nerve  cells  that  send  their  axones  into  the  marginal  tract. 

The  white  nerve  tissue  consists  mainly  of  myelinated  nerve  fibers 
supported  by  neuroglia  and  a  little  white  fibrous  tissue.  These  are 
divided  into  columns  and  tracts.  In  each  half  of  the  cord  there  are 
three  columns,  ventral,  lateral  and  dorsal.  The  ventral  column  lies 
between  the  ventral  median  fissure  and  the  ventral  nerve  roots;  the 
lateral  column  lies  between  the  ventral  and  dorsal  nerve  roots;  the 
dorsal  column  lies  between  the  dorsal  nerve  root  and  the  dorsomedian 
septum.  Connecting  the  ventral  columns  across  the  midline  is  the 
white  commissure  (commissura  alba)  that  lies  between  the  ventral 
median  fissure  (ventrally)  and  the  gray  commissure  (dorsally). 

Each  column  consists  of  tracts,  some  of  which,  however,  do  not 
extend  the  full  length  of  the  spinal  cord.  The  ventral  columns  are 
the  following: 

1.  The  sulcomarginal  tract  (fasciculus  lectospinalis)  borders  the 
ventromedian  fissure,  consists  of  descending  fibers  from  the  corpora 
quadrigemina  of  the  opposite  side  and  is  seen  in  the  cervical  part  of 
the  cord. 

2.  The  direct  pyramidal  tract  {fasciculus  cerebrospinalis  anterior) 
lies  lateral  to  the  preceding  and  consists  of  descending  fibers  from  the 
motor  cells  of  the  cerebral  cortex.  It  represents  undecussated 
fibers  (10  to  15  per  cent.)  of  the  oblongata  but  they  ultimately  cross 
to  the  opposite  ventral  horn  through  the  white  commissure  at  vari- 


THE    SPINAL    CORD 


367 


ous  levels.     It  does  not  extend  below  the  midthoracic  segments  of 
the  cord. 

3.  The  vestibulospinal  tract  (fas.  vestibulospinalis)  consists  of 
descending  fibers  from  the  vestibular  nuclei  of  the  brain  stem,  that 
end  in  the  ventral  horn  of  the  cord  as  far  as  the  sacral  region. 

4.  The  ventral  ground  bundle  (fasc.  anterior  proprius)  lies  at  the 
medial  side  of  the  ventral  horn.  It  consists  of  intersegmental  asso- 
ciation fibers  of  the  ventral  cells  of  the  same  and  opposite  sides 
(ascending  and  descending). 

5.  The  ventral  spinothalamic  tract  (fasc.  spinothalamicus  anterior) 
lies  in  the   intermediate   zone   of   the  ventral  columns,  consists  of 


Fig.  262. —  Diagram  of  the 


tracts  of  the  spinal 


origin  or  termination. 


ascending  axones  of  the  cells  of  the  opposite  dorsal  horn  that  pass 
through  the  white  commissure  and  ascend  to  end  in  the  thalamus. 
These  fibers  convey  touch  and  pressure  impressions  from  the  opposite 
side  of  the  body. 

The  lateral  column  is  more  extensive  and  contains  more  tracts. 

1.  The  olivospinal  tract  (fasc.  olivospinalis)  lies  at  the  side  of,  or  in 
the  ventral  root  region  and  consists  of  descending  axones  from 
the  cells  of  the  olivary  nucleus  (in  the  oblongata) ;  they  end  around 
the  ventral  horn  cells.     This  tract  is  found  in  the  cervical  segments. 

2.  The  superficial  ventrolateral  spinocerebellar  tract  (of  Gowers') 
(fasc.  spinocerebellaris  anterior)  is  at  the  periphery  of  the  cord  and 
consists  of  axones  from  the  cells  of  the  dorsal  horn  of  the  opposite 


368  THE    NERVE    SYSTEM 

side  that  cross  through  the  white  commissure  and  ventral  horn  to 
form  this  tract.  These  fibers  ascend  to  the  cerebellum  through  its 
brachium  conjunctivum  and  constitute  ascending  fibers  that  convey 
muscle  sense  impressions,  chiefly  from  the  opposite  side  of  the  body; 
they  are  concerned  with  reflex  actions. 

3.  The  superficial  dorsolateral  spinocerebellar  tract  (fasc.  spino- 
cerebellarls  posterior)  extends  from  the  preceding  to  the  dorsal  root 
zone.  It  consists  of  the  axones  of  the  nucleus  of  Clarke  from  (he 
same  and  opposite  sides.  These  ascend  and  enter  the  cerebellum 
through  the  restiform  body  and  convey  also  muscle  sense  impressions 
and  are  concerned  with  reflexes. 

4.  The  crossed  pyramidal  tract  (fasc.  cerebrospinal  is  lateralis)  is 
very  extensive  and  lies  medial  to  the  preceding.  This  consists  of  the 
descending  axones  (85  to  90  per  cent.)  of  the  motor  cells  of  the  cerebral 
cortex  that  have  decussated  in  the  oblongata.  They  enter  the  ven- 
tral horn  at  various  levels  and  terminate  about  the  cells  there  that 
form  the  ventral  roots  of  the  spinal  nerves  especially.  This  tract 
continues  to  the  fourth  sacral  segment. 

5.  The  lateral  ground  bundle  (fasc.  lateralis  proplus)  lies  along  the 
lateral  margin  of  the  ventral  and  dorsal  horns.  It  consists  of 
intersegmental  association  fibers  (ascending  and  descending)  that 
arise  in  the  cells  of  both  horns  and  end  at  various  levels  above  and 
below  their  origin. 

Between  the  above-mentioned  tracts  is  an  area  called  the  mixed 
lateral  tract.     Here  several  tracts  have  been  isolated. 

6.  The  rubrospinal  tract  (fasc.  rubrospinalis)  consists  of  axones 
that  descend  from  the  cells  of  the  red  nucleus  of  the  midbrain  to  end 
about  the  cells  of  the  ventral  horn. 

7.  The  tectospinal  tract  (fasc.  tcctospinalis)  consists  of  descending 
axones  from  the  cells  of  the  corpora  quadrigemina  that  end  about  the 
cells  of  the  ventral  horn. 

8.  The  fasciculus  spinotectalis  consists  of  ascending  axones  of  the 
cells  of  the  dorsal  horn  and  ends  in  the  corpora  quadrigemina. 

9.  Ventral  and  dorsal  spinothalamic  tracts  (fasciculi  spinothalamics 
anterior  el  posterior)  comprise  ascending  axones  of  cells  of  the  dorsal 
horn  of  the  opposite  side  that  end  in  the  thalamus.  The  ventral  one 
conveys  impressions  of  touch  and  pressure  from  the  opposite  side 
while  the  dorsal  ones  (mixed  with  the  fibers  of  Govvers'  tract)  convey 
impressions  of  heat,  cold  and  pain  from  the  opposite  side. 

The  tracts  of  the  dorsal  column  are  as  follows: 

1.  The  fasciculus  gracilis  (Colli)  occupies  the  medial  portion  of  the 
column  along  the  dorsal  septum.  It  consists  almost  entirely  of  the 
axones  of  the  cells  in  the  ganglia  of  the  dorsal  roots  of  the  spinal 
nerves.  It  comprises  those  fibers  representing  the  sacral,  the  lum- 
bar and  last  eight  thoracic  nerves.     The  sacral  fibers  are  nearest 


SPINAL    CORD  369 

the  dorsal  septum  and  the  highest  thoracic  are  nearest  fasciculus 
cuneatus.  There  is  really  no  functional  difference  between  the 
fibers  of  this  tract  and  the  fasciculus  cuneatus,  the  latter  represent- 
ing fibers  that  enter  the  cord  merely  at  a  higher  level.  Most  of 
these  fibers  ascend  some  of  them  terminating  in  the  gray  substance 
of  the  dorsal  horn  at  various  levels;  others,  representing  fibers  from 
all  the  spinal  nerve  roots  of  this  tract,  extend  the  length  of  the  cord 
and  end  in  the  nucleus  gracilis  of  the  oblongata.  The  descending 
fibers  will  be  considered  under  the  tracts  of  Schultze,  Flechsig  and 
septomarginal  of  Bruce. 

2.  The  fasciculus  cuneatus  (Burdachi)  lies  lateral  to  the  preceding 
and  represents  axones  of  the  cells  in  the  ganglia  of  the  upper  thoracic 
and  cervical  nerves.  They  correspond  to  the  preceding  and  are 
merely  of  a  higher  level. 

3.  The  dorsal  ground  bundle  (fasc.  posterior  proprius)  is  another 
intersegmental  association  tract.  It  consists  of  the  axones  of  some 
of  the  cells  in  the  dorsal  horn  that  pass  to  the  tract  and  branch 
T-like  and  so  ascend  and  descend  for  a  short  distance  and  reenter 
the  gray  substance. 

4.  The  comma  tract  of  Schultze  (fasc.  inlcrlascicularis)  lies  deep 
between  the  fasciculis  gracilis  and  cuneatus.  It  consists  of  the  short 
descending  branches  of  the  fibers  that  form  the  two  above  fasciculi. 
These  descend  for  a  short  distance  and  enter  the  gray  of  the  dorsal 
horn. 

5.  The  oval  tract  of  Flechsig  {tractus  cervicolumbalis  of  Edmger)  is 
another  such  tract  situated  in  the  fasciculus  gracilis  at  the  dorsal 
median  septum.     This  is  best  seen  in  the  lumbar  region  of  the  cord. 

6.  The  septomarginal  tract  (fasc.  septomarginal  of  Bruce)  is 
another  group  of  descending  fibers  along  the  dorsal  septum  but  close 
to  the  gray  commissure.  These  tracts,  four,  five  and  six,  are  con- 
sidered to  be  of  an  associative  nature. 

7.  The  marginal  tract  (fasc.  posterolateral  is  of  Spitzka  arid  Lissauer) 
is  a  small  bundle  of  fibers  among  the  dorsal  root  fibers  just  after 
they  enter  the  cord.  It  consists  of  the  axones  of  some  of  the  cells  of 
the  ganglia,  that  do  not  enter  the  dorsal  fasciculi  proper  but  continue 
up  the  spinal  cord  as  the  marginal  tract  to  end  around  the  cells  of 
the  substantia  gelatinosa  after  a  course  of  only  three  or  four  seg- 
ments; some  of  these  fibers  may  possibly  end  around  the  cells  of  the 
ventral  and  dorsal  horns. 

The  dorsal  columns  are  the  most  complex  of  the  cord.  It  will  sim- 
plify them  to  consider  the  course  of  the  fibers  that  enter  the  dorsal 
roots  of  the  spinal  nerves. 

1.  Most  of  these  latter  fibers  form  the  fasciculi  cuneatus  and 
gracilis;  these  fibers  divide  into  ascending  and  descending  branches. 
The  ascending  branches  are  of  variable  length  some  ending  soon  in 


370  THE    MERYE    SYSTEM 

the  gray  of  the  dorsal  horn  and  others  ending  in  the  same  way  at 
higher  levels.  Some  ascending  fibers  of  each  spinal  nerve  continue 
to  the  oblongata  and  end  in  the  nuclei  cuneatus  and  gracilis.  The 
descending  branches  that  form  the  oval,  comma  and  septomarginal 
tracts  end  in  the  gray  substance  of  the  dorsal  horn. 

2.  Many  fibers  after  entering  the  dorsal  root  zone  course  along 
the  medial  side  of  the  gray  of  the  dorsal  horn  and  enter  it  to  terminate 
around  the  cells  of  the  same  level.  These  latter  cells  represent 
neurons  that  form  various  tracts  of  the  lateral  column  and  are  also 
concerned  in  the  reflex  arc. 

3.  Some  fibers  of  the  dorsal  roots  enter  into  the  formation  of  the 
marginal  tract  and  terminate  about  the  cells  of  the  substantia 
gelatinosa  and  perhaps  around  other  cells  of  the  ventral  and  dorsal 
horns. 

The  various  cell  groups  and  the  formation  of  the  various  tracts  of 
the  spinal  cord  are  diagrammatically  represented  in  Fig.  262. 

The  fiber  tracts  consist  of  extrinsic  fibers:  (a)  that  arise  outside 
of  the  cord  and  traverse  it  or  end  in  it;  (b)  fibers  that  arise  in  the 
cord  and  pass  out  of  it.  Under  (a)  are  the  tracts  of  Goll  and  Bur- 
dach,  the  crossed  and  direct  pyramidal  tracts,  vestibulospinal,  olivo- 
spinal, some  of  the  mixed  lateral  and  marginal  tracts;  the  direct 
cerebellar  and  Gowers'  tracts,  and  parts  of  the  mixed  lateral  tracts 
come  under  (b). 

The  intrinsic  fibers  are  those  that  arise  and  end  in  the  cord  as  the 
three  ground  bundles. 

THE  BRAIN 

The  brain,  or  encephalon,  is  an  ovoid  mass  of  gray  and  white  nerve 
tissues  that  occupies  the  cranial  cavity.  It  reaches  its  highest  de- 
velopment in  man.  It  is  the  seat  of  the  intellect  and  special  senses 
and  presides  over  motion,  respiration,  circulation,  etc.  Its  measure- 
ments are  as  follows:  Frontooccipitally  6.4  to  6.8  inches  (16  to  17 
cm.),  laterally  5.2  to  5.6  inches  (13  to  14  cm.);  height  5  inches 
(12.5  cm.).  The  average  weight  of  the  adult  male  brain  is  1400 
grams  and  of  the  female  1250  grams.  At  birth  the  weight  in  the 
male  is  400  grams  and  in  the  female  380  grams.  It  usually  doubles 
by  the  end  of  the  first  year  and  trebles  by  the  end  of  the  fourth  or 
fifth  year;  it  almost  reaches  its  maximum  by  the  end  of  the  eighth 
or  ninth  year.  From  that  time  the  growth  in  weight  is  slow  and 
ceases  about  the  eighteenth  or  twentieth  year.  The  brain  begins 
to  lose  weight  after  the  sixtieth  year  and  very  rapidly  from  seventy 
to  eighty  years.  The  important  factors  that  affect  brain  weight  are 
age,  sex,  race,  intelligence,  skull  form  and  body  weight. 

In  regard  to  race  the  Caucasians  have  the  heaviest  and  the  Aus- 
tralians the  lightest.     There  is  considerable  variation  in  the  Cau- 


THE    BRAIN 


371 


casian  race.  In  regard  to  intelligence,  the  brains  of  the  highly  in- 
tellectual individuals  will  weigh  on  the  average  100  grams  more. 
Brains  weighing  under  1000  grams  in  the  male  and  900  grams  in  the 
female  are  usually  considered  too  low  for  mental  integrity. 

The  brain  consists  of  a  number  of  divisions:  (1)  the  cerebrum, 
comprising  the  cerebral  hemispheres  and  a  number  of  lesser  structures; 
second,  the  cerebellum;  third,  the  brain  stem,  comprising  the  midbrain, 
the  pons  and  tegmental  portion  and  the  oblongata.  The  brain  as  a 
whole  when  viewed  from  above,  exhibits  two  lateral  masses,  the  hemi- 


h 


Olfactory  tract Ot 


showing  the  attachn 
From  a  photograph. ) 


spheres,  separated  by  a  deep  cleft,  the  longitudinal  fissure  {fissura 
longitudinalis  cerebri).  The  frontal  pole  is  rather  narrow  but  not 
pointed.  The  parietooccipital  region  in  the  broadest  and  most 
massive,  while  the  occipital  pole  is  rather  sharply  pointed.  The 
superior  and  lateral  surfaces  show  severalrather  deep  clefts  or  fissures 
and  a  number  of  smaller  clefts  or  sulci;  these  separate  the  various 
lobes  and  convolutions  from  one  another.  The  size  and  number  of 
these  convolutions  depends  upon  the  degree  of  intelligence.  When 
the  hemispheres  are  separated  a  whitish  band,  quite  extensive  fronto- 
occipitally,  is  seen  at  the  bottom  of  the  fissure  connecting  the  two 
hemispheres;  this  is  the  corpus  callosum,  or  intercerebral  commissure. 
The  cerebellum  is  not  visible  in  this  view. 

The  under,  or  ventral  surface  (basis  cerebri),  is  also  called  the 


372  THE    NERVE    SYSTEM 

base.  Going  from  before  backward  the  following  parts  are  seen:  the 
frontal  lobes  separated  by  the  longitudinal  fissure  and  upon  each  side 
of  the  fissure  an  olfactory  bulb  and  tract.  Just  behind  the  tracts, 
across  the  midline,  lies  the  optic  chiasm  and  farther  to  the  side  the 
temporal  lobes  which  are  separated  from  the  frontal  lobes  by  the 
sylvian  fissure.  Just  behind  the  chiasm  is  the  tuber  and  stalk  of  the 
pituitary  body;  to  the  rear  of  the  tuber  lie  the  two  corpora  albican- 
tia,  one  upon  each  side  of  the  midline.  This  represents  the  extent  of 
the  cerebrum  upon  the  basal  surface. 

Behind  the  corpora  albicantia  is  a  rather  deep,  triangular  space, 
the  posterior  perforated  space,  bounded  laterally  by  two  large  diverg- 
ing whitish  masses,  the  crura  cerebri.  Appearing  from  the  medial 
side  of  each  crus  (in  the  above  space)  is  a  nerve,  the  oculomotor,  or 
third  cerebral  nerve.  These  structures  constitute  the  midbrain  por- 
tion of  the  brain  stem. 

Behind  the  posterior  perforated  space  and  partially  covering  the 
crura  cerebri  is  a  broad  mass  of  transversely  coursing  fibers,  the 
pons;  at  its  lateral  boundaries  in  front  is  seen  a  large  nerve  upon  each 
side,  the  trigeminus,  or  fifth  cerebral  nerve;  at  its  posterolateral 
boundary  are  noted  two  nerves,  the  facial,  or  seventh  and  the  audi- 
tory, or  eighth  nerves.  Coming  out  between  the  pons  and  the  crus 
on  each  side  is  the  trochlearis,  or  fourth  nerve;  at  the  inferior  border 
of  the  pons  and  near  the  midline  is  seen  the  abducens,  or  sixth  nerve. 
On  each  side,  the  pons  continues  as  a  thick  rope-like  mass  that 
enters  the  corresponding  cerebellar  hemisphere;  these  two  masses 
constitute  the  middle  cerebellar  peduncles  or  brachia  pontis. 

Behind  the  pons  is  a  tapering  structure  that  is  continuous  with  the 
spinal  cord.  This  is  the  oblongata.  Out  of  the  first  fissure  to  the 
side  of  the  median  groove  the  hypoglossus,  or  twelfth  nerve,  is  seen  to 
emerge,  while  farther  to  the  side  are  seen  the  roots  of  the  glosso- 
pharyugcus  (ninth),  vagus  (tenth  )and  accessorius  (eleventh)  nerves. 

At  the  sides  of  the  oblongata  and  completely  covered  by  the  occip- 
ital pole  of  the  cerebrum  are  the  two  hemispheres  of  the  cerebellum, 
separated  from  each  other  in  the  midline  by  a  fissure. 

The  dorsal  surface  of  the  midbrain,  pons  and  oblongata  region  are 
completely  hidden  by  the  cerebrum  and  cerebellum. 

When  the  cerebellum  is  raised  and  the  pia  removed  a  shallow, 
diamond-shaped  fossa,  the  fourth  ventricle  is  exposed.  This  is 
bounded  below  by  the  diverging  inferior  cerebellar  peduncles  and 
above  by  the  converging  superior  cerebellar  peduncles. 

When  the  cerebral  hemispheres  are  raised  from  the  cerebellum  the 
pineal  body  and  the  corpora  quadrigemina  are  exposed.  The  pineal 
body  lies  in  front  of  and  between  the  two  anterior  quadrigeminal 
bodies.     These  will  all  be  considered  under  the  midbrain. 

It  is  customary  to  give  the  external  anatomy  of  each  part  with  its 


THE    BRAIN 


373 


Olfactory  bulb. 

Optic  N.  - 
Oculomotor  II. 

IriyeminaJ 'M. 
Facial  fj. 

Vagal  N. 
Accessory  N 


Optic  chiasm 


Trochlear//, 
-tons 

fibcluce/15  A/. 
Auditor}/  N. 
Glossopharyngeal 'IV. 
HypojIossaJ  N- 


OblonyaJa 


Cerebellum 

Fig.   264. — Diagram  of  the  ventral  surface  of  brain  showing  the  attachments  of  the  cerebral 


X 

y& 

C     -^ , 

A 

*2 

-w-** 


Fig.  265. — Left  lateral  aspect  of  the  brain  with  the  arachnoid,  pia  and  vessels  intact.     (From 
a  photograph). 


374 


THE    NERVE    SYSTEM 


internal  anatomy  immediately  following.  It  seems  more  practical 
to  give  the  external  anatomy  of  each  part  in  sequence  connecting  the 
external  landmarks  as  much  as  possible,  and  then  to  give  the  internal 
anatomy  and  carry  it  through  in  the  same  connected  manner. 

The  parts  of  the  brain  are  often  described  as  forebrain,  midbrain 
and  hindbrain.  It  seems  more  practical  to  describe  the  parts  under 
cerebrum,  cerebellum  and  brain  stem  and  will  be  taken  up  in  that  way. 

THE  BRAIN  STEM 

The  brain  stem  is  continuous  with  the  spinal  cord  and  as  it  shows 
less  differentiation  and  is  the  next  direct  part  it  will  be  first  con- 


optic  chiasma 


interpeduncular 


accessory  nerve 
medulla  oblongata 
of  the  pyramids 

(.Sobotla  and  McMu 


sidered.     Its  parts  from  below,  upward  are  oblongata,  pons  and  teg- 
mental portion  of  the  pons  and  the  midbrain. 

The  oblongata  (medulla  oblongata)  is  about  i  inch  (2.5  cm.)  in 
length  and  is  a  connecting  link  between  the  spinal  cord  and  higher 
centers.  It  is  smallest  at  the  spinal  cord  end  and  gradually  increases 
in  its  dimensions  toward  its  base.     At  the  spinal  cord  end  it  meas- 


THE    OBLONGATA 


375 


ures  about  10  mm.  in  both  dimensions;  at  the  pontile  end  it  measures 
17  to  18  mm.,  transversely,  and  about  15  mm.  dorsoventrallv.  It  is 
flattened  from  before  backward  and  is  directed  nearly  vertically, 
resembling  an  inverted,  flattened,  truncated  cone.  It  presents 
ventral,  lateral  and  dorsal  areas  and  certain  grooves. 

The  ventral  area  contains  only  the  pyramid  [pyramis,  or  fasciculus 
cerebrospinalis  anterior)  and  is  divided  longitudinally  by  the  ventro- 


•mediate  portion) 


root  filaments  of  vagus,  ri 
and  glossopharyngeal           *  "  \?^i 

restiform  body 
pyramid 

taberadam  cineream'     t",'"\    fl 
root  filaments  of  accessary  ner\-» 

if 

J)    *„ 

anterior  root  filaments  of    *  \  i    H     %fu 

cervical  nerve  II          '(j^^^H 

anterior  lateral  sulcus-'    ^^^^HS 

posterior  lateral  salens        spinal 

'§       .  ainea  te  tubercle 
M        fasciculus  euneatas 
1.      posterior  intermediate  salens 
1        posterior  root  filaments 
of  cervical  nerve  II 

Fig.   2^7. — Brain  stem,  lateral  view 

.     (Sobotta  and  McMurrich.) 

median  groove  (fissura  mediana  anterior)  that  terminates  at  the  fora- 
men cecum.  This  groove  is  not  continuous  as  it  is  crossed  and  in- 
terrupted by  bundles  of  fibers  passing  from  one  side  to  the  other 
constituting  the  pyramidal  decussation  (decussatio  pyramidiun).  At  a 
little  distance  to  the  side  of  the  ventromedian  groove  is  another,  the 
ventrolateral  sulcus  (sulcus  lateralis  anterior).  The  mass  of  fibers  be- 
tween these  two  grooves  is  the  pyramid.  Those  fibers  of  the  pyra- 
mid that  cross,  or  decussate  (85  to  90  per  cent.)  constitute  the 
crossed  pyramidal  tract  of  the  spinal  cord.  The  remaining  fibers 
continue  down  the  same  side  to  the  appropriate  levels,  then  cross  to 


376 


THE    NERVE    SYSTEM 


the  opposite  side  through  the  white  commissure  of  the  cord;  these 
libers  constitute  the  direct  pyramidal  tract  of  the  spinal  cord.  Be- 
tween the  pons  and  the  upper  end  of  the  pyramid  the  abducens  nerve 
is  seen  to  emerge. 

The  lateral  area  of  the  oblongata  contains  the  olivary  body,  the 
lateral  column  and  certain  nerve  roots.  The  olivary  body  (oliva) 
is  about  the  size  and  shape  of  an  olive  pit,  that  is,  about  ]2  inch 
(12  mm.)  long;  it  is  situated  at  the  upper  end  of  the  lateral  area 
and  represents  the  position  of  the  inferior  olivary  nucleus. 


Dorsal  groove 
Fig     268  —  Dissei  tion  showing  the  dorsal  aspect  of  the  brain  stem  with  the  corpora  striata 
and  dentate  nuclei  intact.     (From  a  photograph.) 

The  lateral  column  is  in  part  the  continuation  of  some  of  the  lateral 
tracts  of  the  spinal  cord,  i.e.,  the  direct  cerebellar,  Gowers'  and  the 
lateral  ground  bundle.  Below  (caudad)  the  olive  it  is  well  marked, 
being  located  between  the  ventrolateral  and  dorsolateral  grooves. 
Near  the  olive  it  is  crossed  and  hidden  by  the  external  arcuate  fibers 
that  pass  to  the  dorsal  area. 

Between  the  olive  and  the  pyramid  are  seen  the  roots  of  the  hypo- 
glossal nerve  emerging  from  the  ventrolateral  groove.  In  the  dorso- 
lateral groove  are  seen  the  roots  of  the  vagal  and  glossopharyngeal 
nerves,  above,  and  the  roots  of  the  accessory  nerve,  below. 


THE    PONS  377 

The  dorsal  area  is  more  complicated.  In  its  lower  (caudal)  two- 
thirds  in  the  midline,  is  the  dorsomedian  groove  (fissura  mediana 
posterior),  which  ends  above  at  the  lower  angle  of  the  fourth  ventricle. 
This  is  bounded  upon  each  side  by  a  club-shaped  elevation,  the  nu- 
cleus gracilis;  the  upper  end  of  this  is  expanded  and  is  called  the  clava. 
The  nucleus  gracilis  is  bounded  laterally  by  the  dorsal  paramedian 
groove  (sulcus  intermedins)  to  the  outside  of  which  is  the  nucleus  cune- 
atus;  this  is  bounded  laterally  by  the  dorsolateral  groove  (sulcus 
lateralis  posterior).  These  two  nuclei  occupy  the  lower  two-thirds  of 
the  dorsal  area.  Between  the  upper  end  of  the  nucleus  cuneatus  and 
the  lateral  area  lies  an  eminence  the  tuberculum  rolandi  (tuboculum 
cincreum);  this  eminence  lies  in  the  dorsolateral  groove  and  causes  it 
to  fork  at  this  point.  The  upper  part  of  the  dorsal  area  in  the  midline 
is  the  lower  part  of  the  fourth  ventricle,  while  the  lateral  part  of  the 
area  is  represented  by  quite  a  mass  of  fibers  called  the  restiform  body, 
or  inferior  cerebellar  peduncle  (corpus  rest i forme);  these  two  peduncles 
constitute  the  lateral  boundaries  of  the  lower  half  of  the  fourth  ven- 
tricle. This  peduncle  consists  of  the  direct  cerebellar  tract  of  the 
spinal  cord  and  the  superficial  and  deep  arcuate  fibers  of  the  oblongata. 
The  superficial  arcuate  fibers  appear  from  the  ventromedian  groove 
and  sweep  laterally  and  dorsally  over  the  olive  in  a  sheet-like  manner 
occasionally  covering  the  entire  olive.  The}-  continue  dorsally  and 
assist  in  the  formation  of  the  restiform  body. 

THE  PONS  AND  THE  TEGMENTAL  PART  OF  THE  PONS 

The  pons,  or  bridge  (Fig.  266),  represents  the  broad  band  of  fibers 
on  the  ventral  surface  of  the  middle  part  of  the  brain  stem.  It  is 
not  sharply  demarcated  from  the  tegmental  part  upon  section.  It 
represents  the  transverse  fibers  that  connect  the  cerebellar  hemi- 
spheres with  each  other  through  the  nuclei  pontis  and  constitutes 
a  cerebellar  commissure.  It  is  about  1  inch  (2.5  cm.)  from  side  to 
side  and  also  from  above  downward;  it  extends  laterally  to  the  root 
of  the  trigeminus  nerve  on  each  side.  Along  the  midline  its  presents 
the  basilar  groove  (sulcus  basilaris)  in  which  lies  the  basilar  artery. 
Along  the  lower  border  of  the  pons  three  cerebral  nerves  are  seen; 
near  the  midline  is  the  abducens  and  at  the  side  the  facial  and  audi- 
tory nerves,  at  the  upper  edge  of  the  restiform  body.  At  the  sides 
the  pons  fibers  become  massed  into  a  cylindrical  band  that  passes 
into  each  cerebellar  hemisphere;  these  are  the  middle  cerebellar 
peduncles  (brachia  pontis).  Emerging  through  the  lateral  border  of 
the  pons  is  the  trigeminal  nerve  constituting  the  arbitrary  lateral 
boundary  of  the  pons  and  the  beginning  of  the  brachium  pontis. 

The  tegmental  part  of  the  pons,  or  pars  dorsalis  pontis,  cannot 
be  seen  from  the  ventral  surface.  If  a  knife  be  passed  fron tally, 
dorsal    to    the   pons   and    this   structure    lifted  off,   the   tegmental 


378  THE    NERVE    SYSTEM 

part  approximately,  will  be  exposed;  it  seems  to  be  a  continuation 
of  the  oblongata  and  by  some  is  well  called  the  preoblongata.  The 
dorsal  part  of  this  portion  of  the  brain  stem  shows  the  upper  half  of 
the  fourth  ventricle.  At  the  lateral  angles  of  this  space  are  seen  the 
massive  middle  cerebellar  peduncles;  the  lateral  boundaries,  above, 
are  the  converging  superior  cerebellar  peduncles  (brachia  conjunctiva) 
that  also  overhang  and  form  a  part  of  the  roof  of  the  fourth  ventricle. 
The  fourth  ventricle,  or  rhomboidal  fossa  (ventriculus  quart  us), 
represents  the  canal  of  the  spinal  cord  laid  open  and  the  walls  at 
the  sides  stretched  so  as  to  form 
a  diamond-shaped  fossa.  It  is 
nearly  vertical  in  direction.  The 
roof  is  very  thin,  possessing  prac- 
tically no  nerve  tissue,  and  is  rein- 
forced by  the  pia;  that  portion  over 
the  lower  half  of  the  ventricle  is 
called  the  inferior  medullary  velum 
(velum  medullare  inferius),  while  that 
over  the  upper  half  constitutes  the 
superior  medullary  velum,  or  valvule 
(velum  medullare  superius).  Ordi- 
narily the  cerebellum  hides  the  fourth 
ventricle  completely. 

The  so-called  floor  is  nearly  verti- 
cal in  direction  and  represents  the 
dorsal  surface  of  the  pars  dorsalis 
pontis  and  oblongata;  it  consists  of 
gray  nerve  tissue.  It  shows  a  median 
longitudinal  furrow  and  is  divided 
into  upper  and  lower  triangles  by 
some  nerve  fibers  that  cross  the  middle  of  the  space  transversely 
to  pass  into  the  median  furrow;  these  fibers,  the  acoustic  strice 
(strim  medullaris)  may  be  absent,  but  when  present  approximately 
separate  the  oblongatal  part  of  the  ventricle  from  the  tegmental, 
or  pontile  potion. 

In  the  upper  triangle  near  the  midline  and  the  acoustic  striae  is 
an  eminence,  the  collicidus  facialis  (cmincntia  mediana);  just  below 
and  lateral  is  a  depressed  area,  the  superior  fovea.  Above  the  emi- 
nence, toward  the  apex  of  the  triangle,  is  a  slate-colored,  slightly 
depressed  area,  the  locus  carnleus;  the  cells  in  this  area  are  pig- 
mented by  the  substantia  fcrruginea. 

In  the  lower  triangle  just  below  the  acoustic  striae  is  the  area  acus- 
tica  (better  area  vestibularis).  Medially  and  below  this  is  a  triangu- 
lar depression,  the  trigonum  vagi  (ala  ciuerca)  and  between  this  and 
the  median  groove  is  seen  a  tapering  elevation,  the  trigonum  hypo- 


-The  so-called  "flo 

fourth  ventricle. 


THE    MIDBRAIN  379 

glossi.  These  tapering  elevations,  at  the  lower  angle  of  the  ventricle, 
constitute  the  calamus  scriptorius  (point  of  a  pen). 

Between  the  lower  margin  of  the  trigonum  vagi  and  the  lower 
boundary  of  the  ventricle  is  a  narrow  space,  the  area  postrema;  this 
is  separated  from  the  trigonum  vagi  by  the  funiculus  separans,  a 
clear  ridge. 

The  lower  lateral  boundaries  of  the  fourth  ventricle  are  the  diverg- 
ing restiform  bodies;  at  the  lateral  angles  are  the  two  middle  pedun- 
cles; the  upper  lateral  boundaries  are  the  converging  superior 
peduncles  that  also  form  a  small  part  of  the  roof  in  this  region. 

The  fourth  ventricle  communicates  caudally  with  the  spinal  canal 
and  above  it  is  continuous  with  the  aqueduct  of  Sylvius,  or  iter.  It 
represents  a  lymph  space  and  communicates  with  the  subarach- 
noid space  by  means  of  an  opening  in  the  roof  of  the  lower  triangle, 
the  foramen  of  Majendie.  The  roof  at  the  lateral  angles  possesses 
small  openings  called  the  foramina  of  Luschka.  At  the  sides  of  the 
ventricle  are  the  lateral  recesses  (recessi  lateralcs)  that  communicate 
with  the  subarachnoid  space  upon  the  ventral  surface  (at  the  sides) 
between  the  acoustic  and  hypoglossal  nerves  by  means  of  the 
apertura  lateralis  ventriculi  quarti. 

THE  MIDBRAIN 

The  midbrain,  the  upper  part  of  the  brain  stem,  comprises  the 
crura  cerebri,  the  posterior  perforated  space,  the  corpora  quadrigemina, 
the  medial  geniculate  bodies,  the  brachia  and  the  aqueduct  of  Sylvius. 
It  is  about  %  inch  (18  mm.)  in  length. 

The  crura  cerebri  (pedunculi  cerebri)  are  seen  upon  the  ventral 
surface;  each  crus  is  a  large,  whitish,  cylindric  mass  of  nerve  fibers 
which  starts  at  the  upper  border  of  the  pons,  but  at  a  more  dorsal 
level,  and  passes  upward  (frontally)  and  laterally  into  the  cerebrum. 
It  represents  the  chief  bulk  of  the  midbrain.  Between  the  diverging 
crura  is  a  triangular  depressed  area  called  the  posterior  perforated 
space  (interpeduncular  space).  This  is  so  called  because  of  the  large 
number  of  small  openings  that  transmit  vessels  into  the  interior  of 
the  brain  of  this  region.  Along  the  medial  side  of  each  crus  is  the 
oculomotor  sulcus  (sulcus  oculomotorius)  from  which  emerges  the 
oculomotor  nerve.  Near  the  pontile  border  of  the  lateral  margin 
of  each  crus  is  the  trochlear  nerve. 

Upon  each  side  of  the  midbrain  are  seen  the  crus,  the  medial 
geniculate  body,  and  the  superior  and  inferior  brachia. 

The  internal  geniculate  body  (corpus  geniculatum  mediale)  is  a 
small  oval  eminence  on  the  side  of  the  midbrain.  It  is  connected 
with  its  fellow  of  the  opposite  side  by  the  commissure  of  Gudden. 
It  also  represents  an  intermediate  nucleus  in  the  auditory  pathway. 

The  superior  brachium  (brachium  quadrigeminum  superius)  is  a 


38o 


THE    NERVE    SYSTEM 


band  of  libers  at  the  upper,  medial  part  of  the  midbrain .  It  consists 
of  fibers  of  the  optic  tract  that  terminate  in  the  superior  quad-rigem- 
inal  body  and  also  of  fibers  that  pass  to  the  lateral  geniculate  body. 
The  inferior  brachium  (brachium  quadrigeminum  inferius)  lies  at 
the  side  of  the  upper  quadrigeminal  body  and  disappears  under  the 
medial  geniculate  body.  It  represents  fibers  of  the  auditory  path- 
way from  the  inferior  quadrigeminal  body. 


mammillary  hotly 


optic  chiasma  ) 


(Sobotla  and  McMur 


The  dorsal  surface  of  the  midbrain  exhibits  the  corpora  quadrigemina, 
or  colliculi;  of  these  there  are  four,  two  superior  and  two  inferior,  and 
they  are  separated  from  one  another  by  a  transverse  and  a  longi- 
tudinal furrow.     The  latter  is  in  the  midline. 

The  superior  quadrigemina  are  oval  in  shape,  yellowish  gray  in 
color  and  are  the  larger.  Above,  in  the  median  groove  that  sepa- 
rates them,  lies  the  pineal  body.  They  are  centers  connected  with 
eye-muscle  reflexes,  resulting  from  optic  and  auditory  impulses. 

The  inferior  quadrigemina  are  nearly  hemispherical  in  shape  and 
lighter  in  color  than  the  preceding.  They  are  nuclei  in  the  pathway 
of  auditory  impulses. 


THE    CEREBELLUM 


38l 


The  superior  and  inferior  quadrigemina  rest  upon  the  lamina 
quadrigemina  which  really  constitutes  the  dorsal  wall  of  the  mid- 
brain. 

The  iter,  or  aqueduct  (aqueduct us  cerebri),  is  a  narrow  canal  con- 
necting the  third  and  fourth  ventricles.  Its  shape  varies  somewhat 
in  different  parts  and  it  lies  nearer  the  dorsal  than  the  ventral  sur- 
face of  the  midbrain. 


\ 

^^__ 

1 

\^ 

Lenticular  nucleus 
Caudate  nucleus 
Internal  capsule 

Thalamus 
Corpora  quadrigem 
Valvula 
Brachiu::; 

Dentate  nucleus 
Fourth  ventricle 


Dorsal  groove 

Fig.    271. — Dissection  showing  the  dorsal  aspect  of  the  brain  stem  with  the  copora  striata 
and  dentate  nuclei  intact.      (From  a  photograph.) 

THE  CEREBELLUM 

The  cerebellum  lies  in  the  posterior  fossa  of  the  skull  under  cover 
of  the  occipital  pole  of  the  cerebrum  from  which  it  is  separated  by 
the  shelf  of  dura  called  the  tentorium  cerebelli.  It  averages  165 
grams  in  the  male  and  155  grams  in  the  female,  reaching  its  greatest 
weight  between  the  twenty-fifth  and  thirty-fifth  years.  It  repre- 
sents a  coordinating  center  and  might  well  be  called  the  balancing 
brain. 

The  cerebellum  consists  of  two  lateral  lobes,  or  hemispheres,  and 
a  middle  lobe,  or  vermis.  The  two  hemispheres  are  separated  from 
each  other  ventrally  by  a  groove,  the  vallecula,  into  which  the  oblon- 
gata, tegmental  portion  of  the  pons  and  the  midbrain  fit.  Dorsally 
the  hemispheres  are  less  widely  separated. 


382 


THE    NERVE    SYSTEM 


The  vermis  and  each  hemisphere  present  a  superior  and  an  inferior 
surface.  The  superior  surface  of  the  vermis  consists  of  the  following 
lobes,  from  before  backward:  (a)  Hngula  cerebelli;  (b)  lobus  centralis; 


Fig.  272. — Superior  surface  of  the  cerebellum.     {From  a  pnoiograpli.) 

(c)  c  id  men;  (d)  declive.  The  lobes  of  the  superior  surface  of  each 
hemisphere  represents  a  continuation  of  these  with  the  exception  of 
the  lingula.     The  central  lobe  is  continued  into  each  hemisphere  as 


Fig.  273. — Frontal  ' 


'  of  the  cerebellu 


(From  a  photograph.) 


the  ali  lobidi  centralis.  The  admen  continues  as  the  lobus  culminis. 
The  declive  continues  as  the  lobus  lunatus.  In  addition  to  these 
lobes  the  last  of  those  of  the  superior  surface  is  the  posteroinjcrior 
lobe. 

Upon  the  inferior  surface  of  the  vermis  the  following  lobes  are 


THE    CEREBRUM  383 

noted  from  behind  forward:  (a)  tuber;  (b)  pyramis;  (c)  uvula;  (d) 
nodulus.  Upon  each  hemisphere  in  the  same  order  are  the  (a) 
posteroinferior  lobule;  {b)  biveniral  lobule;  (c)  tonsilla;  (d)  flocculus. 

The  fissures  of  the  cerebellum  all  run,  in  general,  transversely 
and  are  eight  in  number  forming,  thus,  nine  lobes. 

The  cerebellum  is  connected  to  the  rest  of  the  nerve  system  by 
its  three  pairs  of  peduncles.  The  inferior  peduncles  (corpora  resti- 
forme)  connect  the  cerebellum  with  the  spinal  cord,  the  oblongata 
and  the  cerebral  nerve  nuclei.  The  middle  peduncles  (brachia  pontis) 
the  largest,  consist  mainly  of  fibers  that  connect  one  cerebellar 
hemisphere  with  the  other  through  the  nuclei  pontis.  The  superior 
peduncles  [brachia  conjunctiva)  are  the  smallest  and  consist  chiefly 
of  fibers  that  connect  the  cerebellar  cortex  with  the  midbrain, 
especially. 

THE  CEREBRUM 

The  cerebrum  comprises  the  cerebral  hemispheres,  the  corpora 
striata,  the  callosum,  olfactory  tracts  and  bulbs  and  the  following 
structures  usually  classified  as  diencephalon:  the  thalami,  the  epiphy- 
sis, the  corpora  albicantia,  tuber,  hypophysis,  optic  chiasm  and  tracts 
and  the  lateral  geniculate  bodies. 

Viewed  dorsally  only  the  cerebral  hemispheres  are  seen.  When 
these  are  separated  in  the  midline,  the  callosum  is  exposed.  If  the 
cerebral  hemispheres  are  raised,  then  the  epiphysis  and  velum  inter- 
positum  are  shown  covering  the  thalami  and  third  ventricle.  The 
lateral  geniculate  bodies  are  also  seen  laterally  placed.  Ventrally 
are  seen  from  behind  forward,  the  corpora  albicantia,  the  tuber 
cinereum  and  hypophysis,  the  optic  chiasm  and  tracts,  and  the  ol- 
factory tracts  and  bulbs. 

The  ventral  structures  will  be  considered  first. 

The  corpora  albicantia  are  two  small,  whitish  bodies  situated  close 
together,  one  on  each  side  of  the  midline  in  the  interpeduncular 
space.     These  are  nuclei  in  the  olfactory  pathway. 

The  tuber  cinereum  is  a  hollow,  conical  structure  lying  just  in 
front  of  the  corpora  albicantia.  Its  cavity  constitutes  the  infun- 
dibular recess  of  the  third  ventricle.  Connected  with  the  lower  end 
of  the  tuber  is  the  hypophysis. 

The  hypophysis,  or  pituitary  body,  is  a  small  glandular  structure 
suspended  from  the  lower  end  of  the  tuber  by  means  of  a  small 
stalk.  It  consists  of  two  divisions  the,  anterior  lobe,  or  prehypophysis, 
and  a  posterior  portion,  the  posthypophysis.  The  former  is  epithelial 
in  structure  and  is  derived  from  the  oral  epithelium;  the  posthypophy- 
sis is  a  direct  derivative  of  the  nerve  system.  These  two  parts  are 
bound  together  by  a  common  capsule. 

The  optic  chiasm  lies  just  in  front  of  the  tuber  and  is  formed  by 


3»4 


THE    NERVE    SYSTEM 


the  convergence  of  the  optic  nerves  here,  attended  by  a  decussation 
of  some  of  their  fibers.  The  nerve  fibers  from  the  nasal  portion  of 
each  retina  cross  to  the  opposite  side  of  the  brain  while  those  from 
the  temporal  side  of  the  retina  continue  on  the  same  side.  This 
produces  the  chiasm  and  decussation.  The  fibers  on  each  side  then 
continue  as  a  flattened  band  called  the  optic  tract  of  which  some  of 
the  fibers  pass  to  the  lateral  geniculate  body,  others  to  the  puhinar 
of  the  thalamus  and  the  remainder  to  the  superior  quadrigemina. 
These  fibers  constitute   the  lateral  root  of  the  optic  nerve.     The 


Olfactory  bulb 

•r 

Olfactory  tract 

Oculomotor__JM( 

m  ■ 

nerve              ^^^E 

Abducens__H^H 

lirrvt'             K.      *» 

Glossopharyn-    j^^\ 
geal  and        ^^        \ 
vagal  nerves 

th 

Hypoglossal  nerve  ^ 

bv     H  < 

/Opt.. 


A^ 


-Ventral   aspect  of  the  brain  showing  the  attachment  of  the  cerebral 
Ft  >»i  a  photograph.) 


medial  root,  or  infracomtnissure  of  Gudden,  are  independent  of  these 
fibers  and  connect  one  medial  geniculate  bod}-  with  the  other  through 
the  chiasm  but  constitute  no  part  of  the  true  optic  pathway. 

The  lamine  tenninalis  is  a  thin  layer  of  gray  nerve  tissue  just 
behind  the  optic  chiasm,  extending  upward  into  the  cerebrum  in 
front  of  the  optic  thalami  and  anterior  commissure;  it  separates 
these  from  the  cerebral  hemisphere  in  front.  It  represents  the  fron- 
tal end  of  the  original  neural  tube.  The  preceding  structures  con- 
stitute the  hypothalamus. 

The  lateral  geniculate  body  (corpus  geniculatum  laterale)  is  seen 
in  a  lateral  view  and  lies  just  in  front  of  the  medial  geniculate  body 
of  the  midbrain  and  represents  a  way-station  of  visual  impulses  in 
the  optic  pathway.  It  represents  a  part  of  the  thalamus.  These 
bodies  constitute  the  metathalamus. 


THE    THALAMI    AND    EPIPHYSIS 


385 


The  thalami  lie  under  cover  of  the  cerebral  hemispheres  and  velum 
interpositum.  When  exposed  each  is  a  large,  ovoid  mass  of  gray 
nerve  tissue  separated  from  its  fellow,  in  the  midline,  by  a  vertical 
cleft,  the  third  ventricle.  The  posteromedial  part  constitutes  the 
puhinar.  The  ventricular  surface  is  smooth  and  shows  an  area 
where  the  two  thalami  are  united  across  the  midline,  making  the 
middle  commissure  (massa  intermedia).  Above  this  and  arching  over 
the  entire  surface  is  a  narrow  ridge  showing  where  the  dorsal  and 


Septum  pellucidu 


Posterior  commissure 


Optic  chiasm 

Hypophysi 
Corpus  mammil: 


th  ventricle 
medullar; 


Oblongata 

-Median  sagittal  section  of  the  brain  showing  the  medial  surface  of  the  right  half. 
{From  a  photograph.) 


medial  surfaces  meet  and  where  the  velum  interpositum  is  attached. 
The  thalamus  is  a  nucleus  in  the  optic  pathway  as  well  as  in  the 
general  sensor  pathway,  from  the  tegmentum  to  the  cerebral  cortex 
(touch  pain,  temperature,  muscle  sense  and  emotional). 

The  epiphysis,  or  pineal  body,  is  a  small,  reddish  body  lying  between 
the  superior  quadrigeminal  bodies  at  the  caudal  end  of  the  roof  of  the 
third  ventricle.  Its  cavity  is  called  the  epiphyseal  recess  and  is  an 
extension  of  the  third  ventricle. 

The  velum  interpositum  is  a  thin  membrane  roofing  the  third  ven- 
tricle and  covering  the  dorsal  surface  of  the  thalami.  This  repre- 
sents the  bulk  of  the  roof  of  the  third  ventricle  and  no  nerve  tissue 
develops  here.  It  is  a  thin  epithelial  layer  and  is  reinforced  by  pia 
with  its  blood-vessels  called  the  tela  ckorioidea.  The  tela  forces  this 
epithelial  layer  in  as  two  ridges  with  blood-vessels  and  these  consti- 
tute a  part  of  the  chorioidal  plexuses. 


386  THE    NERVE    SYSTEM 

Just  in  front  of  the  superior  quadrigemina  and  between  the  caudal 
ends  of  the  thalami  is  a  small  triangular  area  called  the  trigonum 
babe  u  nice.  This  contains  some  nerve  cells,  the  ganglion  habenuliB. 
The  axones  from  these  cells  form  the  fasciculus  retroflexus  and  termi- 
nate in  the  ganglion  inlerpeduncidare  of  the  interpeduncular  space. 
The  ganglion  habenula?  is  a  way-station  in  the  olfactory  pathway. 

The  epiphysis,  velum  and  trigonum  habenulae  constitute  the 
cpithalamus. 

The    third   ventricle   (vcntriculus  tcrtius)   is  a  vertical,   cleft-like 
space  between  the  two  thalami.     It  communicates  caudally  with  the 
iter  and  frontally  and  laterally  with  the  lateral  ventricles,  in  the 
cerebral  hemispheres,  by  means  of  the  foramina  of  Monro. 
CEREBRAL  HEMISPHERES 

The  cerebral  hemispheres  constitute  about  six-sevenths  of  the 
brain  weight.  The  hemicerebri  are  separated  from  each  other,  in 
the  midline,  by  the  median  longitudinal  fissure  [fissura  longitudinalis 
cerebri)  at  the  bottom  of  which  is  seen  the  callosum  which  connects 
these  hemispheres  with  each  other.  The  cerebral  hemispheres  are 
connected  with  the  rest  of  the  brain  mass  by  means  of  the  internal 
capsule. 

Upon  examining  each  hemicerebrum  the  lateral,  or  external  surface 
is  seen  to  be  convex  while  the  media!  surface  is  flattened  above  and 
hollowed  out  below  in  the  temporal  lobe  region.  Each  of  these 
exhibits  little  folds  called  convolutions  which  are  separated  form  each 
other  by  fissures,  or  sulci.  The  main  fissures  are  important  land 
marks  in  the  cerebral  topography  and  serve  to  separate  more  or  less 
completely  the  various  lobes  from  one  another. 

The  lobes  are  frontal,  parietal,  occipital,  temporal  and  central  in  each 
hemisphere.     The  interlobar  fissures  bound  these  lobes  fairly  well. 

Fissures. — Upon  the  lateral  surface  are  seen  the  following  inter- 
lobar fissures: 

i.  The  Sylvian  fissure  (fissura  cerebri  lateralis)  is  about  2}<i  inches 
(6  cm.)  long  and  is  seen  at  the  base  and  side  of  the  frontal  end  of  the 
cerebrum.  It  is  the  deepest  fissure  and  varies  from  15  mm.  at  its 
beginning  to  2$  to  30  mm.,  at  its  deepest  part.  It  extends  back- 
ward and  upward  and  serves  to  separate  the  frontal  and  parietal 
lobes,  above,  from  the  temporal  lobe,  below.  It  consists  of  stem, 
posterior,  ascending  and  anterior  horizontal  rami.  When  its  lips  are 
separated,  the  insula,  or  island  of  Rcil  (central  lobe)  is  exposed.  The 
insula  is  surrounded  by  the  circuminsular  fissure  (sulcus  circidares). 

2.  The  central  fissure  (fissura  centralis)  starts  upon  the  medial  sur- 
face and  then  extends  obliquely  downward  and  forward  on  the  lateral 
surface,  in  a  sinuous  manner,  for  about  4  inches  (10  cm).  It  makes 
an  angle  of  about  710  with  the  midline  and  separates  the  frontal 
from  the  parietal  lobe. 


THE    FISSURES    AND    LOBES    OF    THE    CEREBRUM  387 


V^' 


^.Occipital  lobe 


Temporal  lobe 

Lateral  cerebral  fissure  (Sttviusl  Oblongata 

Fig.   ^76. — Left  lateral  aspect  of  the  brain  with  the  membranes  removed.      (Fr 


Fig.   277- — Main  Assures  and  lobes  of  the  lateral  erebral  hemisphere. 


388  THE    NERVE    SYSTEM 

3.  The  occipital  fissure  (sulcus  parietooccipitalis)  is  seen  about  5 
cm.  above  the  occipital  pole  and  is  only  partly  represented  upon  the 
lateral  surface.  It  indicates  the  separation  between  the  occipital 
and  parietal  lobes. 

Upon  the  media!  surface  the  following  interlobar  fissures  are  seen: 

1.  The  central  fissure  which  extends  for  about  1  cm.  upon  this 
surface. 

2.  The  occipital  fissure,  or  fossa,  has  its  main  portion  on  this  sur- 
face. It  extends  downward  and  forward  for  3  to  3.5  cm.  and  meets 
the  following  fissure.  It  is  usually  quite  deep  and  separates  the 
medial  surface  of  the  parietal  and  occipital  lobes  completely  from 
each  other. 

3.  The  calcariuc  fissure  (sulcus  calcarinus)  arises  upon  the  medial 
surface  about  1  cm.  above  the  base  of  the  cerebrum  just  internal  to 
the  occipital  pole.  It  passes  upward  and  inward  from  3.5  to  4  cm. 
and  joins  the  occipital  fissure;  these  continue  forward  for  about  3  cm. 
as  the  occipitocalcarinc  fissure.  The  calcarine  fissure  separates  the 
occipital  lobe  completely  from  the  temporal  lobe  while  the  occipito- 
calcarine  fissure  separates  parietal  and  temporal  lobes  incompletely. 
The  occipital  lobe,  or  cuneus  is  embraced  by  the  occipital  and  cal- 
carine fissures. 

4.  The  collateral  fissure  (sulcus  collateral  is)  starts  near  the  occipital 
pole  on  the  temporal  lobe  and  continues  frontally  into  the  temporal 
pole  where  it  may  join  the  rhinal  fissure,  one  of  the  minor  fissures. 

The  super callosal  fissure  (sulcus  cinguli)  starts  in  the  frontal  lobe 
beneath  the  genu  of  the  callosum  a  short  distance  and  then  curves 
over  the  callosum  following  its  curvature  to  the  parietal  lobe  where 
it  is  usually  continued  under  the  same  name;  this  latter  part  was 
formerly  called  the  paracentral  fissure  and  surrounds  the  paracentral 
gyre.     Between  the  collosal  and  cingular  fissures  is  the  gyrus  cinguli. 

Other  lesser  fissures  or  sulci  are  as  follows: 

1.  Frontal  Lobe. — Superior,  middle  and  inferior  frontal,  precentral, 
rostral  and  paracingular  sulci. 

2.  Parietal  Lobe. — Postcentral,  angular,  paroccipital,  intermedial 
and  precuneal  sulci. 

3.  Occipital  Lobe. — Lateral  occipital  and  lunatal  sulci. 

4.  Temporal  Lobe. — Superior,  middle  and  inferior  temporal  sulci. 
Each  lobe  is  divided  into  gyres  or  convolutions  by  the  above 

secondary  fissures. 

The  insula,  or  island  of  Reil,  or  central  lobe  is  concealed  by  the 
lips  of  the  sylvian  fissure.  It  is  tetrahedral  in  shape  and  its  apex 
is  pointed  downward  and  forward.  It  is  surrounded  by  the  circum- 
insular  or  circular  fissure.  Those  parts  of  the  cerebrum  that  cover 
in  the  insula  are  called  opercula,  as  temporal  operculum,  superior 
operculum  (frontal  and  parietal)  and  orbital  operculum. 


THE  OLFACTORY  BULB  AND  TRACT 


389 


The  olfactory  lobes  are  located  upon  the  ventral  surface  of  each 
frontal  lobe.  Each  consists  of  the  olfactory  bulb  and  tract.  The 
olfactory  bulb  (bulbus  olfactorius)  is  a  flattened,  oval  mass  of  a  red- 


Central  fissur 


Cingular  fissure 
\ 


>Vx<Yv 


/  Rai-/   ^  Paracentral  fissu 


FlG.   278. — Medial  aspect  of  the  right  cerebral  hemisphere  showing  the  lobes  and  main  fis- 
sures.     {From  a  photograph.) 


Fig.  -70. — Lobes 


n  fissures  of  the  medial  surface  of  the  right  cerebral  hemisphe 


dish-gray  color  in  relation  with  the  cribriform  plate  of  the  ethmoid 
bone.  Through  the  latter  pass  the  various  olfactory  nla  from  the 
nasal  mucosa  to  end  in  the  bulb. 

Each  olfactory  tract   {tr actus  olfactorius)  is  a  flattened  band  of 
nerve  fibers  extending  backward  from  the  bulb  toward  the  optic 


390  THE    NERVE    SYSTEM 

chiasm  and  then  separating  into  a  medial,  an  intermediate  and  a 
lateral  root.  The  area  at  which  these  arise  is  called  the  trigonum. 
The  intermediate  root  is  short  and  passes  to  the  anterior  perforated 
substance.  The  lateral  root  passes  to  the  uncus,  gyrus  ambiens  and 
gyrus  semilunaris.  The  medial  root  passes  but  a  short  distance  to 
the  area  parolfactoria  and  subcallosal  gyre,  fornix  and  fimbria  and 
hippocampal  gyre. 

The  corpus  callosum  (Fig.  278)  is  the  broad  mass  of  nerve  fibers 
bridging  the  bottom  of  the  intercerebral  cleft  and  connecting  the 
two  cerebral  hemispheres  together.  This  represents  a  commissure. 
It  serves  to  connect  areas  of  the  opposite  sides  of  the  cerebrum  with 
each  other.  Upon  the  dorsal  surface  of  the  callosum  lies  a  very 
thin  layer  of  gray  nerve  tissue  continuous  with  the  cortex  of  the 
hemispheres.  In  this  are  some  longitudinal  fiber  bands  called  the 
stria  longitudinalis  and  stria  medialis.  The  gray  tissue  and  fibers 
represent  a  poorly  developed  supercallosal  gyre. 

When  the  callosum  is  cut  parallel  to  the  longitudinal  fissure,  its 
flattened  arch  is  noted.  It  consists  of  the  thickened  frontal  end 
called  the  genu,  next  a  thinner,  band-like  part,  the  body,  and  lastly 
a  large  occipital  end  called  the  splenium.  The  genu  curves  down- 
ward and  then  sharply  backward,  tapering  rapidly  to  form  the  ros- 
trum that  joins  the  lamina  terminalis.  The  genu  contains  frontal 
fibers.  The  body  is  much  longer  and  narrower  than  either  extrem- 
ity and  contains  the  parietal  fibers.  The  splenium  is  the  thickest 
portion  and  forms  the  occipital  end  of  the  callosum.  It  contains 
the  occipitotemporal  fibers.  It  overlaps  the  midbrain  but  is  sepa- 
rated from  it  by  the  velum  interpositum. 

The  callosum  measures  from  7  to  10  cm.  in  length  and  varies  in 
thickness.  The  genu  is  9  mm.,  the  body  5  mm.  and  the  splenium 
13  to  15  mm.  in  thickness.  The  square  surface  is  about  5.5  sq.  cm. 
in  the  average  brain  but  runs  up  to  10.5  sq.  cm.  in  the  brain  of 
highly  intellectual  individuals. 

The  fornix  lies  underneath  the  callosum.  This  consists  of  a 
bundle  of  longitudinally  directed  fibers  that  describes  a  longitudinal 
arch  on  each  side  of  the  midline.  At  the  top  of  the  arch  the  bundles 
are  side  by  side  and  constitute  the  body  of  the  fornix.  As  they  pro- 
ceed frontally  the  bundles  diverge  and  descend,  each  terminating 
in  the  corpus  albicans  of  the  same  side.  Occipitally  the  bundles 
diverge  more  widely  and  descend  and  then  bend  frontally  continuing 
to  the  uncus  of  the  same  side  as  the  fimbria.  These  separated  bun- 
dles constitute  the  anterior  and  posterior  pillars,  respectively,  of  the 
fornix.  This  structure  is  a  part  of  the  olfactory  pathway.  The 
fibers  of  the  fornix  originate  in  the  hippocampus,  form  the  fimbria 
which  continue  as  the  posterior  pillars,  then  the  body  and  then  the 
anterior  pillars  to  finally  terminate  in  the  corpus  albicans  of  that  side. 


CORTICAL    LOCALIZATION 


391 


The  septum  lucidum  {septum  pellucidum)  lies  between  the  callo- 
sum,  above,  and  the  body  of  the  fornix,  below.  It  consists  of  two 
layers  that  enclose  a  space  called  the  fifth  ventricle,  or  pseudocele. 
This  represents  a  part  of  the  original  longitudinal  fissure  that  lies 
subcallosal  and  the  thin  walls  of  the  septum  constitute  the  medial 
walls  of  the  hemispheres  of  this  area  where  nerve  tissues  fail  to 
develop  in  any  great  quantity. 

The  hippocampus  is  an  elevation  in  the  lateral  ventricle  and  is  in 
relation  with  the  fimbria  as  above  described.  It  constitutes  a  part 
of  the  rhinencephalon. 

Within  each  hemicerebrum  is  an  extensive  and  irregular  cavity 
called  the  lateral  ventricle  (ventrical us  lateralis).  Each  consists  of 
a  body,  frontal,  occipital  and  temporal  extensions,  or  horns.  Each 
ventricle  is  in  connection  with  the  third  ventricle  by  an  opening 
situated  between  the  frontal  end  of  the  thalamus  and  the  under- 
surface  of  the  anterior  pillar  of  the  fornix.  The  opening  is  called 
the  foramen  of  Monro  I  foramen  iiiteneutriculus).  The  ventricles  are 
reservoirs  for  the  cerebrospinal  fluid. 

CORTICAL  LOCALIZATION 

The  various  areas  of  cortical  representation  of  the  special  senses 
and  other  functional  areas  are  indicated  in  Figs.  280  and  281. 


280. — Lateral  surface  of  the  left  cerebral  hemisphere  showing  cortical  localization  of 


i.  The  motor  area  occupies  the  posterior  portion  of  the  lateral 
surface  of  the  frontal  lobe  just  in  front  of  the  central  fissure;  it  ex- 
tends over  upon  the  medial  surface  as  indicated. 

2.  The  general  sensor  area  [tactile,  temperature  and  pain)  lies  in 
frontal  portion  of  the  lateral  surface  of  the  parietal  lobe  just  behind 


392 


THE    NERVE    SYSTEM 


the  central  fissure.     It  has  a  marked  extension  upon  the  medial 
surface  also. 

3.  The  auditory  area  is  located  in  the  upper  part  of  the  lateral 
surface  of  the  temporal  lobe  just  below  the  sylvian  fissure. 

4.  The  visual  area  is  located  in  the  occipital  lobe  partially  upon 
the  lateral  surface  but  mainly  upon  the  medial  surface,  occupying 
the  entire  lobe  (aniens)  here. 

5.  The  olfactory  area  is  upon  the  medial  surface  surrounding  the 
callosum,  including  the  fornix,  fimbria  and  hippocampal  portion  of 
the  temporal  lobe. 

6.  The  gustatory  area  is  located  upon  the  medial  surface  of  the 
temporal  lobe  just  beneath  the  olfactory  area. 


showing  cortical  localization  of 


TOPOGRAPHY  OF  THE  BRAIN 

1.  The  longitudinal  fissure  is  indicated  by  drawing  a  line  from  the 
external  occipital  protuberance  (inion)  to  the  root  of  the  nose 
(glabella). 

2.  The  Central  Fissure. — Start  at  a  point  upon  the  longitudinal 
fissure  line  1  cm.  behind  its  midpoint;  from  this  point  draw  a  line 
downward  and  forward  for  9  to  10  cm.  at  an  angle  of  700  to  71°. 

3.  The  lateral  (sylvian)  fissure  starts  i1.-;  inches  (3  cm.)  behind 
the  external  angular  process  of  the  frontal  bone  and  extends  upward 
and  backward  to  a  point  f$  inch  (2  cm.)  below  the  most  prominent 
part  of  the  parietal  eminence. 

4.  Transverse  Fissure. — Draw  a  line  from  the  inion  to  the  external 
auditory  meatus. 

Kronlein's  Method. — (1)  The  base  line  is  a  horizontal  line  from 


INTERNAL    ANATOMY    OF    THE    BRAIN 


393 


the  lower  border  of  the  orbit  to  the  upper  border  of  the  external 
auditory  meatus.  (2)  Draw  a  horizontal  line  parallel  to  (1)  at  the 
level  of  the  supraorbital  ridge.  (3)  Erect  a  vertical  line  AB,  at 
the  middle  of  the  zygoma.  (4)  Draw  a  vertical  line  CD,  from  the 
posterior  border  of  the  mastoid  process  to  the  midline  of  the  skull. 
(5)  Connect  B  and  D.  (6)  Draw  a  vertical  line  E.  G.  from  the  articu- 
lation of  the  mandible  to  BD.  (7)  Bisect  the  angle  DBH  with  the 
line  BI. 


Fig.   282. — Diagram  of  Kronl 


The  line  DB  represents  the  central  fissure.  BI  represents  the 
sylvian  fissure.  At  B  the  anterior  branch  of  the  middle  meningeal 
artery  may  be  reached  and  at  H  the  posterior  branch.  In  abscess  of 
the  temporal  lobe  trephine  in  the  square  E,  C,  H. 

THE  INTERNAL  ANATOMY  OF  THE  BRAIN 

Having  considered  the  external  anatomy  of  the  parts  of  the  brain 
consecutively  the  internal  anatomy  will  now  be  considered  in  the 
same  manner  by  means  of  trans-sections  at  certain  levels. 

In  the  spinal  cord  the  gray  nerve  tissue  is  placed  internally  in  the 
form  of  a  flitted  H-shaped  column  and  the  white  nerve  tissue  surrounds 
it.  At  the  lower  part  of  the  oblongata  the  relation  is  about  the  same 
but  certain  alterations  are  noticeable  due  to  the  presence  of  the  motor 
and  sensor  decussations,  etc.     The  gray  nerve  tissue  continues  in 


394 


THE    NERVE    SYSTEM 


relation  with  the  canal  and  as  the  canal  opens  out  dorsally  to  become 
the  fourth  ventricle,  the  gray  of  the  roof  fails  to  develop,  so  that  we 
find  only  the  floor  composed  of  gray  nerve  tissue  called  the  ventricular 
gray.  It  is  as  though  the  cord  had  been  split  along  the  dorsal  median 
septum  and  the  two  halves  spread  out  and  the  canal  exposed  as  a 
diamond-shaped  fossa.  As  a  result  of  this  the  motor  cells  are  still 
ventrally  placed  but  mainly  near  the  midline  and  the  dorsal  sensor 


Nuclei 

"■   CerebroA 
Nerves 

0>ive_,_|        '  '     f 

IV        }    Ventricular 
Gray 


Fir..   2R3. — Diagram  of  the 


.Spino-l 
Cr«wj     I 


gangl 


cells  have  been  moved  to  the  side.  This  will  be  noticed  when  the 
cerebral  nerve  nuclei  are  considered.  This  peculiar  condition  of  the 
fourth  ventricle  being  at  the  dorsal  surface  of  the  pons-oblongata  is 
due  to  the  failure  of  development  of  nerve  tissue  in  the  dorsal  wall 
of  the  neural  tube  at  this  region.  Hence  all  nuclei  of  this  part  and 
the  liber  tracts  that  pass  centrifugally  and  centripetally  must  pass 
ventral  to  the  cavity,  thus  placing  this  ventricle  at  the  dorsal  surface. 
It  is  to  be  remembered  that  the  nerve  cells  ventral  to  a  line  drawn 


INTERNAL    ANATOMY    OF    THE    BRAIN    STEM  395 

through  the  spinal  canal  from  side  to  side  are  motor  and  those  dorsal 
are  sensor.  As  the  fourth  ventricle  passes  frontal  into  the  aqueduct 
it  is  as  though  the  slit  cord  had  been  returned  to  its  original  condition 
and  gray  nerve  tissue  surrounds  the  entire  aqueduct.  The  ventral, 
or  floor  part  represents  the  seat  of  the  cerebral  nerve  nuclei. 

The  motor  nerve  cells  do  not  form  continuous  columns  as  in  the 
spinal  cord  but  are  grouped  forming  three  interrupted  columns,  con- 
stituting the  nuclei  of  the  cerebral  nerves.  One  column  [medial 
somatic  column)  is  along  the  median  groove  of  the  fourth  ventricle 
and  aqueduct  and  comprises  the  hypoglossal,  and  abduccns  nuclei. 
Another  column  {lateral  somatic  column)  slightly  lateral  to  the  pre- 
ceding, comprises  the  accessory,  part  of  the  vagal,  the  facial,  and  tri- 
geminal nuclei.  These  two  go  to  voluntary,  or  skeletal  muscle,  in- 
cluding tongue,  pharynx  and  larynx.  A  third  column  (splanchnic 
or  visceromotor)  is  located  further  from  the  midline  and  comprises 
part  of  the  vagal,  glossopharyngeal  and  facial  nuclei.  These  cells 
are  concerned  with  the  movements  of  involuntary  nonstriated  mus- 
cles of  the  viscera  and  their  axones  go  to  sympathetic  ganglia. 
These  cells  represent  the  intermedio-lateral  group  of  the  spinal 
cord. 

The  sensor  cells  do  not  form  a  continuous  column  either  but  form 
isolated  groups  of  nuclei  that  lie  furthest  from  the  midline.  These 
nuclei  of  termination  are  for  both  ordinary  and  special  senses.  The 
olivary,  pontile  and  arcuate  nuclei  are  connecting  links  between  the 
cerebellum  and  the  rest  of  the  nerve  system. 

In  the  third  ventricle  that  lies  frontad  of  and  is  continuous  with 
the  aqueduct,  the  gray  substance  is  practically  lacking  so  that  this 
part  of  the  brain  lies  beyond  the  region  of  the  cerebral  nerve  nuclei. 
In  addition  to  this  central  gray  there  are  numerous  nuclei  scattered 
in  the  white  nerve  tissue,  giving  thus  a  mixed  character  that  does 
not  exist  in  the  cord.  In  the  cerebellum  and  the  cerebrum  the  rela- 
tion is  again  more  distinct,  but  the  gray  here  is  superficial  or  cortical 
while  the  white  is  central  or  medullary. 

THE  BRAIN  STEM 

Oblongata. — In  studying  the  internal  structure  of  the  oblongata 
sections  at  the  motor  decussation,  sensor  decussation  and  midolivary 
levels  will  be  utilized.  These  sections  are  from  ascending  levels  in 
the  order  named. 

Motor  Decussation  (Figs.  284  and  285). — In  the  upper  or  pontile 
part  of  the  oblongata  the  motor  fibers  all  lie  in  a  compact  bundle  in  the 
ventral  area  constituting  the  pyramid.  At  the  lower  (spinal  cord) 
part  of  the  oblongata  these  fibers  are  seen  crossing  the  ventral 
median  groove  in  bundles  constituting  the  pyramidal,  or  motor  de- 
cussation.    Upon  examining  a  section  at  this  level  these  fibers  are 


39^ 


THE    NERVE    SYSTEM 


Nucleus  Cuneatus 


rasciculus  Spmo- 
'ercbellaris  Ventrahs 


Mixed  lateral  Tracts 


Vestibule* -Spinal  and 
Spmo-tna/amic  Tracts      Hyramtdal 


Vhvo  Spinal  Tract 
Ventral  Horn 


Decussation 
Fig.   284. — Section  of  the  oblongata  at  the  level  of  the  motor  or  pyramidal  decussation. 


Vcritro'mcd'zn        <     r^mmid 

ra/horn 
effh*  T\ 

FlG.   285. — Section  of  the  oblongata  at  the  level  of  the  motor  decussation  (Weigert's  stain). 
The  right  half  shows  the  various  fasciculi  and  nuclei  in  outline. 


THE    SENSOR    DECUSSATION'  7)91 

seen  sweeping,  obliquely  dorsolaterally,  from  one  side  of  the  ventral 
fissure  to  the  opposite  side  of  the  oblongata,  cutting  through  the 
ventral  horn  of  gray  tissue  to  the  dorsolateral  region.  These  fibers 
constitute  here  the  crossed  pyramidal  tract  of  the  spinal  cord  and 
comprise  85  to  90  per  cent,  of  the  motor  fibers.  The  remaining 
15  to  10  per  cent,  continue  down  on  the  same  side  as  the  direct 
pyramidal  tract  in  the  cervical  and  upper  portion  of  the  thoracic 
part  of  the  spinal  cord,  where  they  cross  at  various  levels  in  the 
white  commissure  so  that  all  fibers  ultimately  end  in  the  opposite  of 
ihe  cord  from  which  they  originate  in  the  cerebrum.  The  motor 
area  of  gray  represented  by  the  ventral  horn  of  the  spinal  cord  is 
thus  cut  into  two  parts:  (i)  the  isolated  ventral  mass  that  is  gradually 
pushed  more  laterally  and  is  diminished  in  size  at  higher  levels;  (2) 
the  basal  portion  (that  near  the  canal)  which  represents  the  motor 
gray  of  the  floor  of  the  fourth  ventricle  higher  up. 

Dorsally  a  change  is  also  noticeable  on  the  peripheral  part  of  the 
dorsal  horn — the  substantia  gelalinosa  has  become  much  increased 
and  forms  a  projection  on  the  lateral  surface  of  the  oblongata  called 
the  tuberculum  cinereum.  The  remainder  of  the  dorsal  gray  also 
shows  alterations.  Near  the  dorsal  median  septum  an  elongated 
aggregation  of  cells,  the  nucleus  gracilis,  appears  among  the  fibers 
of  the  fasciculus  gracilis.  This  ultimately  produces  an  elevation 
upon  the  dorsal  surface  of  the  oblongata  called  the  nucleus  gracilis. 
A  little  lateral  to  this  another  aggregation,  the  nucleus  cuneatus, 
appears;  this  also  forms  an  elevation  upon  the  dorsal  surface.  It  will 
be  remembered  that  the  fasciculi  gracilis  and  cuneatus  (the  tracts  of 
Goll  and  Burdach)  occupy  the  dorsomedian  area  in  the  spinal  cord 
but  at  this  level  of  the  oblongata  they  are  quite  a  bit  smaller  as  their 
fibers  are  terminating  in  their  respective  nuclei;  in  the  next  level 
these  tracts  will  have  ceased  to  exist  being  replaced  by  these  nuclei. 
The  bulk  of  the  fiber  tracts  of  the  lateral  area  of  the  oblongata  pass 
upward  uninterruptedly  into  the  cerebellum,  quadrigemina  or  thal- 
amus as  the  case  may  be.  These  tracts  comprise  the  several  spino- 
cerebellar, spinothalamic,  rubrospinal,  vestibulospinal,  spinotectalis 
and  converse  tracts.     They  will  be  considered  later. 

Sensor  Decussation  (Fig.  286). — Just  above  the  motor  decussa- 
tion lies  the  sensor  decussation.  In  the  ventral  part  of  the  section 
are  seen  all  of  the  motor  fibers  in  two  compact  bundles,  the  pyramid, 
one  upon  each  side  of  the  ventromedian  groove.  Just  dorsal  to 
these  are  seen  first,  a  thin  flattened  bundle,  the  beginning  lemniscus, 
or  fillet  (lemniscus  medial  is)  and  dorsal  to  that  the  decussating  sensor 
fibers  arising  from  the  nuclei  gracilis  and  cuneatus  of  the  opposite 
sides.  These  added  fibers  here  have  raised  the  canal  to  a  slightly 
higher  (dorsal)  level;  between  the  decussating  fibers  and  the  canal 
lie   the  wedge-shaped   remains   of  the  filaments  of  the  hypoglossal 


398  THE    NERVE    SYSTEM 

nerve  sweeping  ventrally  close  to  the  pyramid.  Lateral  to  these 
nerve  fibers  are  seen  the  remains  of  the  isolated  portion  of  the  ventral 
horns  somewhat  smaller  than  in  the  preceding  section.  In  the  dorsal 
half  of  the  section  the  gray  has  a  peculiar  arrangement.  Near  the 
midline  is  the  slender  nucleus  gracilis  and  just  lateral  the  more 
massive  nucleus  cuneatus  and  then  the  tuberculum  cincreum.  Here 
the  nuclei  form  elevations  upon  the  dorsal  surface  and  the  tracts  of 
Goll  and  Burdach  are  almost  ended.  Superficial  to  the  tuberculum 
cinereum,  in  both  sections,  are  seen  some  nerve  cells  and  nerve  fibers 
constituting  the  descending  nucleus  and  root  of  the  trigeminal  nerve 


::<ic-jr">a''  ft.~c .C.//1.5 


Fig.  286. Section  of  the  oblongata  at  the  level  of  the  sensor  decussation  (Weigerfs  stain). 

The  right  half  shows  the  various  fasciculi  and  nuclei  in  outline. 

{nucleus  traclus  spinalis  nervi  trigemini  and  tractus  spinalis  ncrvi 
trigemini). 

Between  this  and  the  next  section  the  nuclei  gracilis  and  cuneatus 
disappear,  several. new  nuclear  masses,  olivary  nuclei,  appear  and 
the  addition  of  a  great  mass  of  nerve  fibers  (formatio  reticularis) 
between  the  canal  and  the  lemnisci  raises  the  canal  to  such  a  level 
dorsally  that  it  is  practically  exposed  and  constitutes  the  fourth 
ventricle.  This  is  due  to  the  fact  that  the  dorsal  wall  of  this  part 
of  the  neural  tube  develops  no  nerve  tissue  and  that  nerve  tissue 
which  does  form  is  ventrally  placed. 

The  Midolivary  Region  (Fig.  287).— This  section  shows  a  marked 
change.  The  ventral  median  groove  is  broad  but  shallow  and  is 
flanked  by  the  large  motor  tracts,  the  pyramids;  these  are  covered 
externally   (superficially)   by  some  gray  nerve  tissue,   the  arcuate 


THE    MIDOLIVARY    REGION 


399 


nucleus  and  some  nerve  fibers,  the  external,  or  superficial  arcuate 
fibers.  Of  these  arcuate  fibers  some  arise  in  the  nuclei  gracilis  and 
cuneatus  of  the  same  side  and  pass  to  the  cerebellum;  others  arise 
from  the  nuclei  of  the  opposite  side,  decussate  in  the  raphe,  course 
ventrally  and  pass  over  the  surface  of  the  pyramid.  Many  of  these 
fibers  are  interrupted  in  the  arcuate  nuclei  and  then  pass  on  to  the 
cerebellum  by  way  of  the  restiform  body.  Just  dorsal  to  the  pyra- 
mids lie  the  medial  lemnisci  forming  quite  a  thick  bundle  of  longi- 
tudinally coursing  fibers.     These  are  separated  from  each  other  in  the 


Nucleus  of  Hypoglossal 
Fourth  UenTr/clr 
Mrjiart  lonyitudmat  Tascir'i 
TectcspirtaJ 


\  7ff/*t  choi-oiifott  inferior 

^Tractus  satitetrius. 

Descendma  roof  of  vestibu 

Jf eti  form  body 


,  ^eK/P°  3Ci 


Pig.  287. — Sec 


of  the  oblongata  at  the  level  of  the  midolivary  region  (  Weigert's  stain). 
The  right  half  shows  the  various  fasciculi,  nuclei  and  nerves  in  outline. 

midline  by  the  median  raphe  that  extends  dorsally  to  the  ventricular 
gray.  The  raphe  consists  of  a  few  nerve  cells  and  fibers.  Some  of 
the  fibers  run  longitudinally,  others  obliquely  (internal  arcuate  fibers) 
and  still  others  run  dorsoventrally  (belonging  to  the  external  arcuate 
fibers). 

Between  each  lemniscus  and  the  floor  of  the  fourth  ventricle  on 
each  side  of  the  raphe  are  seen  bundles  of  fibers  running  longitudi- 
nally, transversely  and  some  gray  nerve  tissue;  this  constitutes  the 
mass  mentioned  above  as  the  formatio  reticularis.  This  field  is 
divided  by  the  hypoglossal  nerve  roots  into  a  median  area  (formatio 
reticularis  alba)  as  it  contains  little  gray  nerve  tissue;  the  lateral 
part  is  the  formation  reticularis  grisea  as  it  contains  considerable 


4<DO  THE    NERVE    SYSTEM 

gray  nerve  tissue.  The  transverse  fibers  are  chiefly  internal  arcuate 
and  olivocerebellar,  while  the  longitudinal  are  chiefly  association 
fibers  (short  course)  of  the  centers  of  respiration  (nuclei  of  the  facial, 
phrenic  and  vagal  nerves)  derived  from  the  cells  of  the  grisea.  One 
especial  group  of  longitudinal  fibers  just  beneath  the  ventricular 
gray  is  called  the  median  longitudinal  bundle  (fasciculus  lougiludinalis 
medialis).  This  is  a  set  of  longer  association  fibers  that  serves  to 
connect  the  various  cerebral  nerve  nuclei  together  and  corresponds 
to  the  ventral  and  ventrolateral  ground  bundles  of  the  spinal  cord. 
The  fibers  just  ventral  to  this  bundle  constitute  the  fasciculus  tecto- 
spinalis. 

Just  dorsal  to  and  a  little  to  the  side  of  the  pyramid  lies  a  crinkled 
mass  of  gray  containing  white  fibers  and  surrounded  by  white  fibers. 
This  is  the  inferior  olivary  nucleus  (nucleus  olivius  inferior)  which 
produces  the  elevation  upon  the  lateral  surface  of  the  oblongata 
called  the  olive.  Its  opening,  or  hilus,  is  directed  toward  the  raphe 
and  of  the  fibers  seen  entering  and  leaving  some  pass  to  the  olive 
of  the  other  side  while  others  pass  to  the  cerebellum  of  the  opposite 
side  through  the  restiform  body  and  vice  versa.  In  addition,  fibers 
pass  to  and  from  the  olive  to  the  spinal  cord  and  thalami.  The 
dorsal  and  medial  olivary  nuclei  are  detached  parts  of  the  main 
nucleus. 

In  the  dorsal  region  of  this  section  is  seen  the  lower  end  of  the 
fourth  ventricle.  The  roof  is  thin  and  devoid  of  nerve  tissue  and  con- 
stitutes the  tela  choroidea  inferior.  The  floor  of  the  ventricle  con- 
sists of  gray  nerve  tissue  showing  several  aggregations  of  cells,  or 
cerebral  nerve  nuclei.  On  each  side  of  the  midline  lies  the  nucleus 
of  the  hypoglossal  nerve;  just  lateral  lies  a  small  group  of  cells,  the 
nucleus  iutercalatus  (function  not  known).  At  the  side  of  this  lies 
one  of  the  nuclei  of  the  vagal  nerve.  That  part  of  the  vagal  nucleus 
near  the  midline  is  motor  (to  the  heart)  and  the  lateral  portion  is 
sensor.  In  the  lateral  dorsal  mass  is  seen  a  large  group  of  fibers,  the 
descending  root  of  the  auditory  nerve;  just  beneath  this  are  the  nucleus 
and  fasciculus  solitarius;  at  the  extreme  dorsal  portion  is  seen  the 
restiform  body'.  The  latter  structure  contains  the  fibers  of  the  direct 
spinocerebellar  and  cerebellospinal  tracts  of  the  spinal  cord  and  the 
internal  and  external  arcuate  fibers  of  the  oblongata  region.  Be- 
neath these  structures  is  seen  another  nucleus  of  the  vagus,  the  nucleus 
ambiguus  and  the  fibers  of  the  vagus.  This  nucleus  probably  repre- 
sents the  remains  of  the  isolated  portion  of  the  ventral  horn  of  the 
cord  from  lower  sections.  Near  the  side  are  seen  the  nucleus  and 
fibers  of  the  spinal  root  of  the  trigeminal  nerve. 

Pons  and  Pars  Dorsalis  Pontis. — This  portion  of  the  brain  stem  is 
equivalent  to  the  oblongatal  part  plus  a  broad  and  thick  band  of 
transverse  fibers  ventrally  placed;  the  latter  fibers  constitute  the 


THE   INTERNAL    ANATOMY   OF   THE   PONS   REGION 


4OI 


pons.     This  part  of  the  brain  will  be  considered  in  three  sections: 
(1)  lower,  (2)  middle  and  (3)  tipper. 

1.  If  a  section  at  the  lower  end  be  examined  the  ventral  part 
will  be  seen  to  consist  of  a  rather  thick  mass  {pars  basalis  pontis) 
of  transversely  coursing  fibers,  the  pons,  and  two  large  bundles  of 
longitudinal  fibers,  the  pyramids.  In  among  these  fibers  are  seen 
collections  of  nerve  cells  called  the  nuclei  pontis.  The  transverse 
fibers  are  more  abundant  in  man  than  in  any  other  animal.  Most  of 
them  lie  ventral  to  the  pyramidal  tracts  and  serve  to  connect  the 
cerebellar  hemispheres  with  each  other.     At  the  lateral  boundaries 


Nucleus  globosus 


Nucleus  emboliformls 


Nucleus  dentatus 


Beehterew's  nucl 

Deiter's  nucleus 
Spinal  root  of  V  nerve 


Nucleus  of  VII 


conjunctivun 
Corpus 
restiforme 

Nucleus  VI  ni 


Pyramid    Medial  1. 


Fig.   288. — Section  of  the  lower  part  of  the  pons  region. 

of  the  pons  these  fibers  are  collected  into  a  compact  bundle  that 
enters  the  corresponding  cerebellar  hemisphere  as  the  middle  pedun- 
cle (brachium  pontis).  Some  of  the  pons  fibers  end  around  the  cells 
of  the  pontile  nuclei  of  the  same  side  and  some  go  to  the  opposite  side ; 
new  fibers  then  arise  from  these  cells  and  continue  to  the  cerebellar 
hemisphere.  Some  of  the  cells  of  the  nuclei  pontis  are  also  way-sta- 
tions in  the  pathway  of  cerebropontile  fibers  and  new  fibers  arising 
here  pass  to  the  cerebellar  hemispheres.  These  cerebropontile  fibers 
have  a  longitudinal  course. 

In  the  area  just  dorsal  to  the  pons  fibers  are  the  pyramids,  two 
large  compact  bundles  of  longitudinal  fibers  on  their  way  to  the 
oblongata.  Some  of  these  fibers  terminate  in  the  nuclei  pontis 
representing  cerebropontile  fibers.  Dorsal  to  the  pyramids  are  seen  a 
variable  number  of  deeper  transverse  pontile  fibers.  The  arcuate 
fibers  and  nuclei  of  the  oblongata  are  analogous  to  the  pons  fibers  and 
pontile  nuclei. 

Dorsal  to  the  pons  lie  the  fibers  of  the  medial  lemniscus  forming  a 


4-02 


THE    NERVE    SYSTEM 


rather  compact  bundle  upon  each  side  of  the  raphe.  In  higher  sec- 
tions these  lemnisci  diverge  from  the  midline  to  make  room  for 
the  trapezium. 

Pars  Dorsalis  Pontis. — The  lemnisci  separate  the  pons  proper  from 
the  pars  dorsalis  pontis  (preoblongata).  Dorsal  to  the  outer  side 
of  the  lemniscus  is  seen  the  central  tegmental  trad  and  the  superior 
olivary  nucleus  connected  with  the  fibers  of  the  trapezium  (acoustic 
fibers).     Between  the  superior  olivary    nucleus  and  the   formatio 


reticularis  lies  a  bundle  of  fibers  (trapezia!)  that  form  the  trapezium 
of  the  next  level.  This  portion  shows  also  the  formatio  reticularis  on 
each  side  of  the  raphe  with  the  median  longitudinal  bundle  in  its  dor- 
sal area;  between  the  formatio  reticularis  and  the  cavity  of  the  ven- 
tricle is  the  ventricular  gray  substance  in  which  are  seen  certain  cere- 
bral nerve  nuclei. 

Near  the  midline  is  seen  the  nucleus  inscrtus  (Streeter)  that  con- 
tinues up  to  the  aqueduct.  To  the  side  of  this  lies  the  nucleus  of  the 
abducens  nerve;  lateral  to  this  the  principal  vestibular  nucleus  is  noted 
and  beneath  the  gray  the  descending  root  of  the  vestibular  nerve;  at 
the  dorsal  margin  lies  the  upper  end  of  the  rcstiform  body.     Deeper 


THE    INTERNAL    ANATOMY    OF    THE    PONS    REGION 


403 


ventrad  and  over  the  superior  olivary  nucleus  is  the  nucleus  of  the 
facial  nerve,  while  lateral  thereto  are  some  of  the  fibers  of  this  nerve. 
Between  the  facial  nerve  and  the  restiform  body  are  found  the  sub- 
stantia rolandi  and  the  descending  root  of  the  trigeminal  nerve. 

2.  Upon  examining  a  section  through  the  trigeminal  nerve  (middle 
section)  the  ventral  part  of  the  section  exhibits  superficial  and  deep 
fibers  of  the  pons  embracing  the  two  pyramids.  At  the  sides  the 
brachia  pontis  are  still  present.     At  the  junction  of  the  pons  with  the 


Fourth 

Dorsal  longitu- 
dinal fasciculus 
Median  longi- 
tudinal fascic- 
ulus 


Deep   fibers   of 
pons 


r~ 

^k. 

M 

_. 

-^/_ 

< 

-J^ieH*! 

- '*—          4- 

Brachium  con- 
junctivum 

Desc.  motor 
root  of  the  tri- 
geminal nerve 

Sensor  nucleus 
of  trig,  nerve 

Motor  nucleus 
of  trig,  nerve 

Thalmoolivary 
tract 

Lateral  lemnis- 

Brachium 


Fig.   290. — Section  of  the  pons  at  the  level  of  the  origin  of  the  trigeminal  nerve. 


tegmental  part  the  media)  lemnisci  have  been  pushed  to  the  side  and 
replaced  by  the  trapezium,  a  set  of  transversely  directed  fibers  (decus- 
sating) intersperced  with  nerve  cells  (the  trapezia]  nucleus).  These 
fibers  arise  from  the  ventral  and  some  from  the  dorsal  cochlear 
•nuclei  of  the  fourth  ventricle  and  pass  to  the  trapezium  where  some 
end  in  the  nucleus  trapezoideus  of  the  same,  or  opposite  side  while 
others  end  in  the  olivary  nucleus  of  the  same,  or  opposite  side.  The 
new  fibers  from  the  cells  of  these  nuclei  then  cross  to  the  opposite  side 
(if  the  preceding  have  not)  making  the  decussation  complete;  they 
are  then  joined  by  the  new  fibers  from  the  cells  of  the  opposite  side 
and  constitute  the  lateral  lemniscus,  which  will  be  described  later. 
The  trapezium  is  a  part  of  the  auditory  pathway.  Between  the 
trapezium  and  the  lateral  surface  of  the  section  are  seen  the  superior 
olivary  nucleus,  the  fibers  of  the  motor  root  of  the  trigeminal  nerve, 
while  more  ventrally  are  the  brachia  pontis  and  the  sensor  root  of  the 
trigeminal  nerve;  near  the  surface  lies  the  sensor  nucleus  of  the  latter 
nerve. 


404 


THE    NERVE    SYSTEM 


Dorsal  to  the  trapezium  and  in  the  midline  is  the  raphe  with  the 
for  mat  io  reticularis  forming  a  large  field  on  each  side.  Lateral  to  the 
formatio  is  the  motor  nucleus  of  the  trigeminal  nerve,  next  the  mesen- 
cephalic root  of  the  same  nerve  and  upon  the  surface  the  superior  cere- 
bellar peduncle  {brachium  conjunctivum)  forming  also  the  dorsal 
wall  of  the  section  in  this  area.  The  peduncle  is  semilunar  in  shape 
and  consists  chiefly  of  fibers  from  the  cells  of  the  dentate  nucleus  of 
the  cerebellum,  while  the  remainder  are  probably  from  the  cerebellar 
cortex  of  the  opposite  side,  decussating  to  reach  this  side.  These 
fibers  pass  chiefly  to  the  red  nucleus  of  the  midbrain  and  some  con- 
tinue to  the  thalamus. 

In  the  dorsal  portion  of  the  section  the  fourth  ventricle  is  seen 
becoming  narrower  and  is  roofed  by  the  valvula,  or  anterior  medullary 


Fig.   291. — Diagram  of  the  nuclei  of  the  cerebral  nerves  in  the  brain  stem  (lateral 
Motor  nuclei  in  solid  block,  sensor  nuclei  dotted.  ' 


velum.     Beneath  the  ventricular  gray  and  near  the  midline  is  the 
median  longitudinal  fasciculus . 

3.  A  section  through  the  upper  part  of  the  pons  is  more  compact 
and  smaller.  In  the  ventral  area  the  pyramids  are  separated  into 
many  small  bundles  by  the  transverse  pontile  fibers.  At  the  side  of 
the  field  is  seen  the  trigeminal  nerve.  In  the  tegmental  portion 
changes  have  occurred.  In  the  midline  just  dorsal  to  the  pons  fibers 
the  trapezium  has  been  replaced  by  the  decussating  fibers  of  the  bra- 
chia  conjunctiva  while  the  medial  lemniscus  is  now  seen  at  the  side 
and  somewhat  flattened.  Dorsal  to  the  decussating  fibers  is  seen  the 
formatio  reticularis,  lateral  to  which  is  placed  the  brachium  conjunc- 
tivum no  longer  superficial,  as  in  the  preceding  section,  but  rather 
deeply  placed  and  covered  by  the  flattened  band,  the  lateral 
lemniscus.  The  lateral  lemniscus  previously  mentioned  consists  of 
the  ventral  cochlear  fibers  and  nerve  cells  comprising  the  nucleus  of 


THE    INTERNAL    ANATOMY    OF   THE   MIDBRAIN  405 

the  lateral  lemniscus,  apparently  a  continuation  of  the  superior  olive. 
Here  some  of  the  fibers  of  the  lemniscus  end  and  new  ones  arise  from 
the  cells  of  the  nucleus  and  continue,  to  end  in  the  inferior  quadri- 
geminum  and  medial  geniculate  body  and  possibly  in  the  superior 
quadrigeminum.  The  dorsal  median  area  of  the  formatio  reticularis 
is  occupied  by  the  median  longitudinal  fasciculus.  Dorsal  to  this  area 
is  the  ventricular  gray  substance.  In  this  section  the  fourth  ventricle 
is  small  and  entirely  roofed  over  by  the  valvula  that  contains  a 
little  nerve  tissue.  At  the  lateral  boundary  of  the  ventricular  gray 
is  noted  the  mesencephalic  root  of  the  trigeminal  nerve. 

THE  MIDBRAIN 

In  this  portion  of  the  brain  stem  two  sections  will  be  described, 
one  through  the  inferior  quadrigeminal  bodies  and  the  other  at  the 
level  of  the  superior  quadrigeminal  bodies. 


Transverse  section  of  the  midbrain  through  the  inferior  quadrigeminal  bodies. 

The  section  through  the  inferior  bodies  shows  a  marked  change 
over  the  preceding  sections.  Ventrally  are  seen  the  two  crura  cerebri 
(pedunculi  cerebri)  separated  from  each  other  by  the  interpeduncular 
space.  Each  cms  consists  of  a  ventral  area  called  the  crusta  (basis 
pedunculi)  containing  only  motor  fibers  in  three  groups:  (1)  the 
lateral  one-fifth  consisting  of  fibers  from  the  cortex  of  the  temporal 
lobe  of  the  cerebrum  to  the  nuclei  pontis  and  called  the  temporo- 
pontile  tract;  (2)  the  middle  three-fifths  consists  of  the  fibers  from  the 
pyramidal  cells  of  the  motor  area  of  the  frontal  lobe  passing  to  the 
cerebral  nerve  nuclei  and  to  the  spinal  cord  constituting  the  pyram- 
idal tract  previously  mentioned;  (3)  the  medial  one-fifth  consist  of 
fibers  from  the  cells  of  the  frontal  lobe  passing  to  the  nuclei  pontis 
and  called  the  frontopontile  tract.  Dorsally  the  crusta  is  bounded 
by  a  crescentic  mass  of  pigmented  gray  substance  called  the  sub- 
stantia nigra.     This  separates  the  tegmentum  from  the  crusta  and 


406 


THE    NERVE    SYSTEM 


its  cells  send  their  axones  in  various  directions  but  their  function  is 
unknown.  The  substantia  nigra  extends  throughout  the  midbrain. 
The  tegmentum  consists  of  transverse  and  longitudinal  fibers  with 
collections  of  nerve  cells  here  and  there.  It  represents  a  continua- 
tion of  the  tegmental  portion  of  the  pons.  In  the  midline  is  seen  the 
raphe  and  at  the  side,  above  the  substantia  nigra,  lies  each  brachium 
conjunctivum  completing  its  decussation.  Lateral  to  this  is  the 
medial  lemniscus.  Dorsal  to  the  superior  cerebellar  peduncle,  near 
the  midline,  is  seen  the  median  longitudinal  fasciculus,  while  near  the 
surface  is  located  the  lateral  lemniscus  covered  by  the  inferior 
brachium.  Dorsal  to  the  raphe  is  the  aqueduct  gray  substance,  con- 
taining a  small  canal,  the  iter,  or  aqueduct  (aqueduclus  cerebri).     The 


through  the  superior  quadri^c-minal  bodit 


gray  substance  surrounds  the  canal  completely;  in  its  floor,  resting 
upon  the  median  longitudinal  fasciculus,  is  a  collection  of  nerve 
cells,  the  nucleus  of  the  trochlear  nerve.  At  the  side  of  the  gray  is  the 
ftiesencep/ialis  root  of  the  trigeminal  nerve.  Dorsal  to  the  aqueduct 
gray,  on  each  side  of  the  midline,  is  a  rounded  mass  of  gray  nerve 
tissue  covered  by  white  fibers,  the  inferior  quadrigcminal  body 
[colliculus  inferior).  The  nucleus  of  each  body  is  separated  from  the 
aqueduct  gray  by  the  stratum  lemnisci.  The  nucleus  ■  receives 
fibers  chiefly  from  the  lateral  lemniscus.  Its  cells  send  fibers  to  the 
thalamus  and  the  nucleus  represents  a  way-station  in  the  auditory 
pathway. 

In  the  pregeminal  region  the  crusta  and  substantia  nigra  are 
substantially  the  same.  Medially,  at  the  junction  of  the  tegmentum 
and  crusta,  is  a  groove  (sulcus  oculomotorius)  from  which  the  oculo- 
motor nerve  emerges.  In  the  tegmentum  an  important  change  has 
occurred.  Near  the  midline  is  a  large,  reddish,  circular  collection  of 
nerve  cells  called  the  red  nucleus.  The  fibers  of  the  oculomotor 
nerve  course  around  and  through  it.  This  nucleus  receives  fibers 
from  the  cerebral  cortex,  the  corpus  striatum  and  from  the  cere- 


INTERNAL  ANATOMY  OF  THE  PBEGEMTNAL  REGION 


407 


bellum  through  its  brachia  conjunctiva;  most  of  the  fibers  of  the 
latter  end  here.  From  its  cells  fibers  extend:  (1)  to  the  thalamus  and 
the  cerebral  cortex;  (2)  to  the  spinal  cord  as  the  rubrospinal  tract. 
These  latter  fibers  decussate  almost  immediately  and  pass  down  the 
opposite  tegmentum. 

To  the  side  of  the  red  nucleus  lies  the  medial  lemniscus  and  it  is 
smaller  as  many  of  its  fibers  terminate  in  the  superior  quadrigeminal 


Fig.  294. — Diagram  of  the  formation  and  components  of  the 
of  the  brain  stem. 


edian  longitudinal  fasciculu 


body  and  the  remainder  pass  to  the  thalamus  (general  sensor  path- 
way); at  the  side  of  the  lemniscus  lies  the  inferior  bracliium.  Be- 
tween the  two  red  nuclei  is  seen  a  mass  of  decussating  fibers  called 
the  fountain  decussation.  These  fibers  are  derived  from  the  superior 
quadrigeminal  bodies  and  the  cells  in  the  aqueduct  gray,  cross  the 
midline  and  join  the  median  longitudinal  fasciculus  and  pass  to  the 
nuclei  for  the  nerves  of  the  eye  muscles  and  to  the  spinal  centers  for 
movements  of  the  head  and  neck. 


40S  THE    NERVE    SYSTEM 

The  median  longitudinal  fasciculus  (Fig.  294)  occupies,  relatively, 
the  same  position  as  in  previous  sections.  It  corresponds  to  the. 
ventral  ground  bundle  of  the  spinal  cord.  Its  fibers  are  associative 
with  regard  to  many  cerebral  and  spinal  nerve  centers.  It  connects 
especially  the  quadrigeminal  bodies  and  the  sensor  cerebral  nerve 
nuclei  with  the  oculomotor,  trochlear,  abducens  and  facial  cerebral 
nerves.  A  special  nucleus  is  located  in  the  floor  of  the  third  ventricle 
at  its  junction  with  the  aqueduct.  The  fibers  from  this  nucleus 
decussate  immediately  and  cross  through  the  posterior  commissure. 

In  the  dorsal  part  of  the  section  are  the  aqueduct,  surrounded  by 
the  aqueduct  gray,  in  the  ventral  part  of  which  is  the  nucleus  for  the 
oculomotor  nerve.  Dorsal  to  the  gray  are  the  two  superior  quadri- 
geminal bodies  (colliculi  superiores).  Each  body  consists  of  four 
layers  of  alternating  white  and  gray.  The  white  layers  represent 
fibers  of  the  optic  tract  and  some  from  the  occipital  cortex.  Other 
fibers  enter  from  the  lateral  and  medial  lemnisci  (part  of  the  optico- 
acoustic  reflex  pathway). 

INTERNAL  ANATOMY  OF  THE  CEREBELLUM 

As  previously  mentioned,  the  cerebellum  consists  of  two  lateral 
hemispheres  with  an  intermediate  vermiform  lobe  (vermis).  Most  of 
the  gray  substance  is  externally  located  and  the  white  is  internal. 
The  remaining  gray  is  found  in  the  white  as  certain  nuclei,  to  be 
mentioned  later.  In  the  vermis  the  gray  predominates  while  in  the 
lateral  hemispheres  the  white  predominates.  As  the  main  fissures 
and  sulci  run  transversely  and  as  the  gray  is  comparatively  thin 
the  cut  edge  of  the  cerebellum  exhibits  a  peculiar  arborescent  ap- 
pearance; this  is  called  the  arbor  vita"  ccrebelli. 

In  the  white  substance  of  each  lateral  hemisphere  is  a  crinkled 
layer  of  gray  with  a  white  core  called  the  dentate  nucleus  (nucleus 
denial  us).  It  resembles  the  olivary  nucleus  of  the  oblongata  and 
like  it  has  a  hilus  for  the  entrance  and  exit  of  nerve  fibers.  Its  cells 
give  rise  to  most  of  the  fibers  of  the  brachia  conjunctiva  and  it  repre- 
sents a  way-station  in  the  indirect  motor  pathway. 

The  nucleus  embolis  is  small,  lies  just  medial  to  the  preceding  and 
is  analogous  to  the  accessory  olivary  nucleus. 

The  nucleus  globosus  lies  a  little  medial  and  ventral  to  the  embolis 
while  the  nucleus  fastigii  lies  in  the  white  substance  of  the  vermis 
close  to  the  midline. 

There  are  three  pairs  of  cerebellar  peduncles,  inferior,  middle  and 
superior.  The  inferior  peduncles,  or  restiform  bodies,  enter  the 
cerebellum  beneath  the  other  two.  Each  consists  of  afferent  and 
efferent  fibers;  the  afferent  fibers  comprise:  (1)  the  dorsolateral 
superficial  spinocerebellar  tract  (direct  cerebellar)  derived  from  the 
column  of  Clark  (nucleus  thoracis)  of  the  spinal  cord  and  ending 


THE    INTERNAL    ANATOMY    OF    THE    CEREBELLUM 


409 


in  the  gray  of  the  vermis  of  both  (but  chiefly  the  opposite)  sides;  (2) 
the  olivocerebellar  fibers  (internal  arcuate  of  oblongata)  that  arise 
in  the  olivary  nucleus  and  end  in  the  cortex  of  the  vermis  and  hemi- 
spheres and  also  in  the  dentate  nucleus;  (3)  the  external  arcuate 
fibers  from  the  nuclei  gracilis  and  cuneatus  of  both  sides;  (4)  fibers 
from  the  vestibular  and  trigeminal  nuclei;  (5)  cerebellospinal  fibers 
arising  in  the  cerebellum  and  ending  in  the  ventral  horns  of  the 
spinal  cord  {efferent). 

The  middle  peduncle   {brachium  ppntis)   the  largest  consists  of 
fibers  running  in  opposite  directions  across  the  midline  and  consti- 


FlG.  205. — Section  of  the  right  cerebellar  hemisphere  showing  the  dentate  nucleus.      (From 
a  photograph.) 

tuting  a  commissure  connecting  the  two  lateral  cerebellar  hemispheres 
with  each  other.  Most  of  these  fibers  end  in  the  nuclei  pontis  of 
the  same  or  opposite  side  and  new  fibers  from  these  cells  complete 
the  circuit.  In  addition,  some  of  the  fibers  connect  the  cerebellar 
hemispheres  with  certain  cerebral  nerve  nuclei,  especially  the  oculo- 
motor, trochlear  and  abducens  nuclei. 

The  superior  peduncles  (brachia  conjunctiva)  the  smallest,  form 
an  oval  or  concavoconvex  band;  the  fibers  arise  in  the  dentate 
nucleus  of  the  same  side,  chiefly,  with  additional  fibers  from  the 
nuclei  fastigii  of  both  sides.  The  fibers  decussate  in  the  midbrain 
where  most  of  them  end  in  the  red  nucleus,  while  a  few  continue  to 
the  thalamus.  This  peduncle  also  contains  the  ventrolateral  super- 
ficial spinocerebellar  tract  (Gowers').  Its  fibers  instead  of  entering 
the  cerebellum  through  the  inferior  peduncles  continue  into  the 
pars  dorsalis  pontis  and  enter  the  cerebellum  through  the  superior- 
peduncles. 


4io 


THE    NERVE    SYSTEM 


The  cerebellum  contains  other  fibers  than  the  above,  called  the 
fibrrn  proprm.     These  are  commissural  and  association  fibers;   the 
commissural  fibers  connect  the  hemispheres  with  each  other  across 
the  midline  and  pass  through  the  vermis.     The  association  fibers  do 
not  cross  the  midline  but  connect  adjacent  laminae  with  one  another. 
THE  INTERNAL  ANATOMY  OF  THE  CEREBRUM 
A  section  of  the  cerebrum  shows  that  like  the  cerebellum  it  con- 
sists chiefly  of  gray  nerve  substance  externally  {cortex)  and  white 
■        ^  .,„      nerve  tissue  internally  (medulla).    In 

■"V  '    addition,  masses  of  gray  tissue  are 

seen  near  the  ventral  part  of  the 
cerebral  hemispheres  and  are  there- 
fore called  basal  ganglia.  The  in- 
ternal anatomy  is  best  represented 
with  two  sections  one  horizontal,  or 
flatwise  (side  to  side)  about  midway 
between  dorsal  and  ventral  sur- 
faces; the  other  a  frontal  {vertical) 
section  at  the  level  of  the  anterior 
commissure. 

The  horizontal  section  shows  the 
bulk  of  the  gray  externally  and  the 
white  internally  placed,  while  toward 
the  center  are  seen  various  basal 
ganglia.  Just  within  the  lateral 
margin,  near  the  frontal  end,  is  the 
island  of  Reil,  or  central  lobe  {insula). 
Medial  to  this  is  the  periclaustral 
{white)  lamina  covering  the  irregular 
strip  of  gray,  the  claustrum.  This  is 
one  of  the  basal  ganglia  and  probably 
represents  an  isolated  portion  of  the 
cortex  of  the  insula.  Medial  to  the 
claustrum  lies  a  narrow  strip  of 
white  nerve  tissue  the  external 
capsule  and  frontally,  caudally,  and 
dorsally  it  connects  with  the  internal 
capsule  and  represents  fibers  of  an  associative  nature  for  the  cortical 
regions  around  the  insula.  It  contains  a  few  fibers  that  pass  to  and 
from  the  thalamus. 

The  next  medially  placed  structure  is  the  corpus  striatum  consist- 
ing of  two  masses  of  gray,  the  lenticular  and  caudate  nuclei,  separated 
from  each  other  by  the  frontal  limb  of  the  internal  capsule.  The 
caudal  limb  of  the  internal  capsule  separates  the  lenticular  nucleus 
from  the  thalamus. 


Fig.  296. — Horizontal  section  of  the 
Tight  cerebral  hemisphere  through  the 
corpus  striatum.  (From  a  photograph.) 
C,  Caudate  nucleus;  /,  internal  capsule 
(anterior  limb) ;  c,  posterior  limb;  Ins, 
insula;  CI,  claustrum;  OR,  optic  radia- 
tion; Th,  thalamus. 


THE    STRUCTURE    OF    THE    CORPUS    STRIATUM 


411 


The  lenticular  nucleus  {nucleus  lent  if  or  mis)  is  surrounded  by  white 
substance  and  is  shaped  like  a  triangular  pyramid,  or  on  section  it 
resembles  a  biconvex  lens,  hence  the  name.  It  is  divided  into  three 
main  masses  and  each  of  these  has  fine  bands  of  white  giving  a  stri- 
ated appearance  to  the  mass.  The  largest  and  lateral  segment  is 
called  the  putamcn  while  the  other  two  constitute  the  globus  pallidus. 

The  caudate  nucleus  (nucleus  caudatus)  as  the  diagram  shows,  is  a 


/?mysdu,/<: 


/flmySiA 


Fig.   297. — Model    of    the    corpus    striatun 
A,  Lateral  view;  B,  medial  view. 


Fig.  298. — Drawing  of  the  left  internal 
capsule,  viewed  from  above,  showing  its 
component  fibers. 


tail-shaped  mass  of  gray  nerve  tissue.  Owing  to  its  arched  course 
its  sections  present  different  appearances  at  different  levels. 

The  amygdaloid  nucleus  (nucleus  amygdala)  represents  an  isolated 
part  of  the  temporal  cortical  gray  substance  connected  with  the  end 
of  the  caudate  nucleus.     It  is  not  shown  at  this  level. 

The  interna!  capsule  lin  this  section  represents  a  knee-bent  mass 
of  white  nerve  tissue  situated  between  the  lenticular  nucleus,  later- 
ally and  the  caudate  nucleus  and  thalamus,  medially.  It  represents 
the  only  pathway  for  fibers  from  the  cerebral  cortex  to  brain  stem 
and  cerebellum  and  vice  versa.     In  the  early  stage  of  development  of 


412 


THE    NERVE    SYSTEM 


the  nerve  system  the  cerebral  vesicles  are  connected  to  the  primitive 
forebrain  vesicle  around  the  future  foramen  of  Monro  which  later 
becomes  unimportant  functionally.  Soon  the  ventromedial  surface 
of  each  cerebral  vesicle  rests  upon  the  dorsolateral  surface  of  each 
thalamus  and  a  fusion  takes  place,  the  striatothalamic  fusion.  This 
fusion  area  is  the  later  internal  capsule.  The  frontal  limb  contains 
the   thalamofrontal   and   striatofrontal   fibers.     These   fibers   arise 

from  the  cells  of  the  thalamus 
and  end  in  the  lenticular  and 
caudate  nuclei  of  the  corpus 
striatum  and  frontal  lobes  of 
the  cerebrum.  These  are  the 
corticipetal  fibers.  In  addition 
there  are  the  fibers  running  in 
the  opposite  direction  as  the 
frontopontile  (frontal  cortex 
to  pontile  nuclei);  fronto- 
thalamic  (frontal  cortex  to  the 
thalamic  nuclei);  striatothala- 
mic fibers  (from  striate  nuclei 
to  the  thalamic  nuclei).  These 
are  corticifugal  fibers. 

The  knee  portion,  or  genu 
contains  the  fibers  of  the 
pyramidal  tract,  voluntary 
motor  fibers  that  arise  from 
the  pyramidal  cells  of  the 
cortex  of  the  frontal  lobe  in 
front  of  the  central  fissure  and 
pass  through  the  internal 
capsule  to  form  the  pyramids 
previously  mentioned.  The  motor  portion  takes  in  about  half  of 
the  occipital  limb  of  the  internal  capsule.  The  remainder  of  this 
limb  contains  the  sensor  fibers  that  pass  from  the  thalamus  to  the 
cortex  of  the  parietal  lobe,  to  the  general  somatic  sensor  area.  At 
the  extreme  occipital  part  of  this  limb  are:  (i)  fibers  of  the  optic 
radiation  that  course  in  both  directions  between  the  pulvinar  of 
the  thalamus,  the  lateral  geniculate  body  and  the  superior  quad- 
rigeminal  bodies  (on  the  one  hand)  and  the  occipital  cortex  (visual 
area)  on  the  other;  (2)  fibers  of  the  auditory  radiation  passing 
both  ways  between  the  medial  geniculate  and  inferior  quadrigem- 
inal  body,  on  the  one  hand,  and  the  cortex  of  the  temporal  lobe 
(auditory  area)  on  the  other;  (3)  occipitopontile  and  temporopontile 
fibers  from  the  cortex  of  these  lobes  to  the  nuclei  pontis. 

The  thalamus  (Fig.  296)  is  an  important  way-station  in  the  sensor 


Fig.  299. — Frontal  section  of  the  Tight  cere- 
bral hemisphere  through  the  corpus  striatum 
and  internal  capsule.  (From  a  photograph.)  C. 
Caudate  nucleus;  CI,  claustrum;  1.  internal 
capsule;  L,  lenticular  nucleus. 


THE   VENTRICULAR    SYSTEM  413 

and  optic  pathways.  It  receives  impulses  of  muscle  sense,  pain, 
temperature  and  touch  and  transmits  them  to  the  cerebral  cortex 
and  receives  in  return  impulses  from  the  various  parts  of  the  cerebral 
cortex.  It  is  an  emotional  center  under  control  of  the  cerebral  cortex. 
Its  fibers  constitute  the  thalamocortical  and  corticothalamal  groups. 
These  represent  fibers  to  and  from  the  frontal,  parietal  and  occipital 
lobes  and  ventral  fibers  to  and  from  the  temporal  lobe,  island  of  Reil, 
and  lenticular  nucleus. 

The  thalamus  lies  between  the  occipital  limb  of  the  internal  cap- 
sule and  the  midline.  It  consists  of  three  chief  nuclei  separated  from 
one  another  by  white  nerve  tissue;  these  are  the  nucleus  anterior, 
nucleus  medialis  and  the  nucleus  lateralis  (largest). 

A  vertical  or  frontal  section  shows  the  above  structures,  but 
in  a  slightly  different  relation.  The  internal  capsule  shows  no  bend 
but  has  a  regular  course  that  is  oblique  in  direction,  converging 
toward  the  midline.  Beneath  the  lenticular  nucleus  is  seen  the  cor- 
pus callosum  that  represents  a  commissure  connecting  the  cerebral 
hemispheres  with  each  other. 

THE  VENTRICULAR  SYSTEM 

The  ventricular  system  comprises  the  two  lateral  ventricles,  the  fo- 
ramina of  Monro,  the  third  ventricle,  the  aqueduct,  the  fourth  ventricle, 
the  foramen  of  Magendie  and  the  spinal  canal. 

Each  lateral  ventricle  (ventricidus  lateralis)  lies  in  a  cerebral  hem- 
isphere and  comprises  a  body,  and  three  horns,  anterior,  middle  and 
posterior.  The  body  (pars  centralis)  is  situated  underneath  the 
body  of  the  corpus  callosum  and  over  the  caudate  nucleus  and  part 
of  the  thalamus;  it  communicates  at  its  frontal  end  with  the  third 
ventricle  by  means  of  the  foramen  of  Monro  (foramen  intervmtri- 
culare).  The  anterior,  or  frontal  horn  (pars  anterior)  is  short  and 
extends  from  the  foramen  of  Monro,  forward  and  outward  into  the 
frontal  lobe.  The  middle,  descending,  or  temporal  horn  (pars  inferior) 
is  the  largest  and  passes  backward,  outward,  downward,  forward  and 
inward  in  the  temporal  lobe.  The  posterior,  or  occipital  horn  (pars 
posterior)  passes  backward  and  inward  from  the  body  of  the  ventricle 
into  the  occipital  lobe. 

The  third  ventricle  (ventriculus  tcrtius)  is  a  vertical  cleft  in  the  mid- 
line between  the  two  thalami  and  dorsal  to  the  chiasm,  tuber  cin- 
ereum,  corpora  albicantia  and  part  of  the  tegmentum  of  the  crura 
cerebri.  It  is  covered,  or  roofed  by  the  velum  interpositum.  It 
continues  frontally  as  a  slight  evagination,  the  optic  recess;  ventrally, 
it  gives  rise  to  the  infundibular  recess  and  dorsallv,  to  the  epiphyseal, 
or  pineal  recess.  It  communicates  with  each  lateral  ventricle  by  a 
foramen  of  Monro  and  caudally  with  the  fourth  ventricle  by  means 
of  the  aqueduct. 


4M 


THE    NERVE    SYSTEM 


The  aqueduct  or  iter  (aquedudus  cerebri)  lies  in  the  midbrain;  its 
roof  is  the  lamina  quadrigemina  and  its  floor  the  tegmental  part 
of  the  crura  cerebri.  It  is  a  short,  narrow  canal  that  communi- 
cates caudally  with  the  fourth  ventricle  and  frontally  with  the  third 
ventricle. 

The  fourth  ventricle  (vcntriculus  quartiis)  is  a  shallow,  diamond- 
shaped  fossa  in  the  pons  oblongata  region.     Its  floor  (better  ventral 


Occipital  horn 
Fig.  300. — Horizontal  section  of  the  brain  through  the  lateral  ventricles. 

wall)  is  the  tegmental  part  of  the  pons  and  oblongata;  in  the  oblon- 
gata region  it  is  roofed  by  the  tela  chorioidea  inferior  and  in  the 
pons  region  by  the  valvula  and  the  brachia  conjunctiva.  At  the 
frontal  and  caudal  angles  the  fossa  becomes  canal-like  to  continue  as 
the  aqueduct  and  spinal  canal,  respectively.  At  the  lateral  angles 
the  cavity  continues  as  a  narrow  recess  over  each  corresponding  resti- 
form  body  and  these  prolongations  are  called  the  lateral  recesses. 
Openings  here  lead  into  the  subarachnoid  lymph  space  and  these  are 
the  foramina  Lusckkce  (apertura  latcralcs).  The  upper  and  lower  parts 
of  the  roof  do  not  form  a  flat  structure  but  a  gable,  or  peak  under 
the  cerebellum,  so  that  the  ventricle  has  the  greatest  depth  here. 
The  tela  chorioidea  inferior  has  an  opening  near  its  spinal  cord  end 
called  the  foramen  of  Magendie,  which  communicates  with  the  sub- 
arachnoid space.     This  with  the  foramina  of  Luschka  permits  an 


THE    WHITE    SUBSTANCE    OF    THE    CEREBRUM 


415 


interchange  of  cerebrospinal  fluid  between  the  ventricular  system 
and  the  lymph  spaces  of  the  membranes  covering  the  brain.  By  this 
means  an  equilibrium  of  pressure  is  established  inside  and  outside  of 
the  brain  and  spinal  cord. 

The  spinal  canal  is  a  narrow,  tube-like  space  extending  the  length 
of  the  spinal  cord;  it  is  located  in  the  gray  commissure.  It  tends 
to  become  obliterated  more  or  less  after  the  prime  of  life. 

The  entire  ventricular  system  is  lined  with  ependymal  cells  that  in 
the  spinal  cord  are  chiefly  simple  ciliated  cells  and  in  the  ventricles 
simple  squamous,  or  simple  ciliated  elements. 

The  white  substance  of  the  cerebrum  (medulla)  consists  of  my- 
elinated nerve  fibers  that  are  classified  according  to  their  connections, 
into  three  groups:  (1)  projection,  (2)  association,  (3)  commissural. 


Fig.  301. — The  ventricular  system  of  the  brain  represented  in  situ. 

i.  The  projection  fibers  are  those  that  pass  from  the  cortex  to 
lower  centers  (thalamus,  midbrain,  pons,  oblongata)  and  are  centrifu- 
gal in  direction;  to  these  are  added  the  fibers  from  the  lower  centers 
to  the  cerebral  cortex,  the  corticipetal  fibers.  These  fibers  form  the 
bulk  of  the  corona  radiata.  This  is  nothing  more  nor  less  than  the 
fan-shaped  form  assumed  by  the  fibers  from  the  various  cerebral 
convolutions  as  they  pass  to,  or  ascend  from,  the  internal  capsule. 
It  is  the  fan-shaped  collection  of  fibers  dorsal  to  the  internal  capsule 
that  at  a  more  ventral  level  constitute  the  internal  capsule. 

The  corticifugal  fibers  are  the  pyramidal,  or  great  voluntary  motor 
pathway,  the  corticothalamic,  frontopontile,  temporopontile,  and 
the  corticifugal  fibers  of  the  optic  radiation.  All  of  these  indicate 
by  the  name  the  origin  and  termination,  and  their  respective  posi- 
tions have  been  discussed  in  the  internal  capsule  and  the  crura  cere- 
bri; the  pyramidal  tract  has  been  discussed  in  the  pons,  oblongata 
and  spinal  cord. 


416  THE    NERVE    SYSTEM 

The  corticipctal  fibers  comprise  the  thalamocortical,  the  auditory 
radiation  and  the  optic  radiation. 

2.  The  association  fibers  are  short  and  long.  The  short  ones  con- 
nect areas  in  adjacent  convolutions  with  one  another,  or  gyri  rather 
close  together  (arcuate  and  tangential  fibers).  The  long  association 
fibers  connect  areas  remote  from  one  another  in  the  same  cerebral 
hemisphere  as  the  cingulum,  uncinate,  superior  longitudinal  and 
fasciculus  rectus. 

3.  The  commissural  fibers  are  those  that  pass  across  the  midline 
to  connect  areas  of  the  opposite  sides  together.  Under  this  head  are 
found  the  corpus  callosum,  the  hippocampal  commissure  and  the 
anterior  commissure. 

The  corpus  callosum  is  the  largest  commissure  and  consists  of 
fibers  that  cross  the  midline  in  both  directions  at  the  bottom  of  the 
intercerebral  cleft.  The  fibers  form  a  compact  structure  already 
considered  and  these  fibers  spread  out  in  all  directions,  but  unequally, 
so  that  all  parts  of  the  cortex  do  not  receive  the  same  number  of 
fibers.  These  fibers  may  be  direct  axones  of  cells,  or  collateral  of 
the  association,  or  projection  fibers.  It  connects  all  parts  of  the 
cerebral  cortex  with  one  another,  except  parts  of  the  temporal  lobes 
and  the  olfactory  bulbs. 

The  hippocampal  commissure  is  part  of  the  olfactory  pathway. 
It  connects  the  cornu  ammonis  of  the  two  sides  together. 

The  anterior  commissure  is  also  a  part  of  the  olfactory  pathway, 
connecting  the  two  olfactory  bulbs  with  each  other  and  also  con- 
necting the  olfactory  bulb  of  one  side  with  the  temporal  lobe  of  the 
other  side.  Most  of  the  fibers  of  the  commissure  pass  from  one  tem- 
poral lobe  to  the  other,  but  the  exact  point  of  termination  is  not 
known. 

The  various  pathways  will  now  be  considered. 

The  Direct  Motor  Pathway. — This  comprises  but  two  neurons. 
The  parts  concerned  are  the  two  pyramidal  tracts  and  the  motor  por- 
tions of  the  cerebral  and  spinal  nerves. 

The  pyramidal  tract  of  each  side  consists  of  afferent  fibers  that  arise 
from  the  large  and  small  pyramidal  cells  of  the  motor  area  of  the 
cerebral  cortex.  They  pass  down  through  the  corona  radiala  into 
the  internal  capsule  occupying  the  middle  portion  thereof;  the}'  enter 
the  crusta  of  the  crus  cerebri,  then  the  tegmentum  of  the  pons  and 
the  ventral  area  of  the  oblongata;  in  these  three  regions  some  of  its 
fibers  pass  to  the  cerebral  nerve  nuclei  of  origin.  At  the  caudal  end 
of  the  oblongata  85  to  90  per  cent,  of  the  fibers  decussate  to  the  op- 
posite side  of  the  spinal  cord  as  the  crossed  pyramidal  tract  and  then 
end  at  various  levels  around  the  cells  of  the  ventral  horn.  The 
remaining  fibers  continue  down  the  same  side  of  the  spinal  cord,  as 
the  direct  pyramidal  tract,  to  various  levels  in  the  cervical  and  upper 


THE    MOTOR    PATHWAY 


417 


thoracic  region  and  then  pass  through  the  ventral,  or  white  com- 
missure, to  end  in  the  ventral  horn  of  the  opposite  side.  Ultimately 
all  fibers  decussate  before  they  end.  This  ends  the  first  neuron.  The 
second  neuron  comprises  the  cells  of  the  ventral  horn  and  their 
processes  that  form  the  motor  root  of  the  spinal  nerves,  on  the  one 


FlG.  .^02. — Diagram  of  the  neurons  in  the  direct  and  indirect  motor  pathways  and  the  con- 
nections of  the  cerebellum  with  the  brain  stem  and  the  spinal  cord.  Direct. — Neuron  1,  .4  to 
B\  neuron  2.  B  to  C.  Indirect. — Neuron  1.  A  (cerebral  cortex)  to  D;  2,  D  to  E;  3,  E  to  F;  4, 
F  to  g;  5,  «  to  B\  6,  B  to  C. 

hand,  and  in  the  case  of  the  cerebral  nerves  comprises  the  cells  of 
the  various  nuclei  of  origin  and  their  processes  that  form  the  motor 
portion  of  the  cerebral  nerves.  These  axones  pass  out  of  the  gray 
substance,  become  myelinated  and  ultimately  end  directly  in  a  vol- 
untary striated  muscle  fiber.  This  is  the  em!  of  the  second  neuron. 
First  neuron,  a  pyramidal  cell  in  the  motor  cortex  of  the  cerebrum 


4  1. 


THE    NERVE    SYSTEM 


and  its  axone  that  forms  a  part  of  the  pyramidal  tract  and  that 
ends  in  a  cerebral  nerve  nucleus,  or  the  ventral  gray  of  the  spinal 
cord. 

Second  neuron,  the  cell  in  the  nucleus  of  origin  or  in  the  ventral 


Fig.    303. — The  origins,  decussat 


i  and  courses  of  the  fibers  forming  the  media!  and  lateral 
i.     Direct  sensor  pathway. 


gray  of  the  spinal  cord,  and  its  axone  that  ends  in  a  voluntary 
striated  muscle  fiber. 

The  Indirect  Motor  Pathway. — This  is  more  complex  and  com- 
prises six  neurons.  First,  from  the  motor  area  of  the  cerebrum  (say 
right  side)  through  the  pyramidal  tract,  as  above,  to  the  nuclei 
pontis  of  the  same  side  (right) ;  second,  from  the  nuclei  pontis  through 


THE    SENSOR    PATHWAY  419 

the  brachium  pontis  to  the  cerebellar  cortex  of  the  opposite  (left)  side; 
third,  from  the  cerebellar  cortex  to  the  dentate  nucleus  of  the  cere- 
bellum of  the  same  (left)  side;  fourth,  from  the  dentate  nucleus 
through  the  brachium  conjunctivum  to  the  red  nucleus  of  the  opposite 
(right)  side;  fifth,  from  the  red  nucleus  of  that  side  through  the 
rubrospinal  tract  to  the  cerebral  nerve  nucleus,  or  ventral  horn  of 
the  spinal  cord  of  the  opposite  (left)  side.  (The  fibers  of  the  rubro- 
spinal tract  cross  to  the  opposite  side  almost  immediately  after  leav- 
ing the  red  nucleus.)  Sixth,  from  the  cerebral  nerve  nucleus,  or  the 
ventral  horn  gray  to  the  voluntary  striated  muscle  fiber.  As  seen 
above  there  are  three  crossings,  or  decussations,  the  next  to  the  last 
neuron  terminating  upon  the  opposite  side  of  the  body. 

The  Direct  Sensor  Pathway. — In  the  trunk  the  impulses  arise  at 
the  periphery  and  are  conveyed  by  the  sensor  spinal  nerves  to  the 
ganglia  on  the  dorsal  roots.  From  there  they  are  conveyed  into  the 
dorsal  column  of  the  spinal  cord  to  end  in  the  nuclei  gracilis  and 
cuneatus  of  the  oblongata  of  the  same  side.  Some  collaterals  are 
sent  into  the  dorsal  horn  gray.  New  fibers  arise  in  the  nuclei  cune- 
atus and  gracilis  and  immediately  cross,  or  decussate  to  the  opposite 
side,  forming  the  sensor  decussation,  that  lies  just  above,  or  cephalad 
of  the  motor  (pyramidal)  decussation.  These  decussated  fibers 
form  the  medial  lemniscus  that  continue  through  the  oblongata,  pons 
and  midbrain  to  end  in  the  thalamus  of  that  sine.  From  the  thalamus 
new  fibers  convey  the  impulses  through  the  internal  capsule  (posterior 
limb)  to  the  somatic  sensor  area  of  the  cerebral  cortex  (postcentral 
gyre).  In  this  pathway  three  neurons  are  recjuired,  the  first,  from 
the  surface  to  the  nuclei  gracilis,  or  cuneatus  (the  cell  body  lying  in 
the  dorsal  ganglion);  the  second,  from  these  nuclei  to  the  thalamus; 
and  the  third,  from  the  thalamus  to  the  cerebral  cortex. 

Reflex  conduction  may  occur  in  two  ways: 

(1)  Direct. — The  impulse  is  conveyed  into  the  cord  in  the  above 
manner  but  the  fiber  as  it  enters  the  cord  gives  off  collaterals  of  two 
kinds: 

(a)  A  collateral  that  passes  to  the  ventral  horn  of  the  same 
and  opposite  sides  where  it  ends.  The  impulse  then  originates  from 
the  motor  cells  in  that  area  and  is  conveyed  to  the  muscle  which 
moves  unconsciously. 

(b)  As  the  sensor  fibers  enter  the  spinal  cord  they  divide  into 
ascending  and  descending  fibers.  The  ascending  pass  to  the  nuclei 
gracilis  and  cuneatus  and  give  off  collaterals  at  various  levels.  The 
descending  fibers  end  at  various  segments  in  the  dorsal  horn  and  new 
fibers  arise  from  the  cells  here  to  pass  to  the  ventral  horn  of  the  same 
and  opposite  sides.  New  impulses  arise  from  the  motor  cells  here 
and  are  conveyed  to  the  muscles. 

(2)  An  indirect  reflex  path  is  as  follows:  First  neuron,  from  the  peri- 


420 


THE    NERVE    SYSTEM 


pherv  to  the  nuclei  cuneatus  and  gracilis  through  the  dorsal  column 
of  the  spinal  cord.  Second  neuron,  from  these  nuclei  to  the  cerebellar 
cortex  through  the  restiform  body.  Third  neuron,  from  the  cere- 
bellar cortex  to  the  dentate  nucleus  of  the  cerebellum  (same  side). 
Fourth  neuron,  from  the  dentate  nucleus  to  the  red  nucleus  through 
the  brachium  conjunctivum.  Fifth  neuron,  from  the  red  nucleus 
through  the  rubrospinal  tract  to  the  ventral  horn  of  the  spinal  cord. 
Sixth  neuron,  through  the  ventral  motor  roots  to  the  muscle.     In 


Fig.  304. — Diagram  of  the  structures  involved  in  a  reflex  action.  .4,  receptive  surface; 
B,  skeletal  muscle;  C.  blood-vessel  and  sympathetic  ganglion;  D.  a  viscus  and  sympathetic 
ganglion;  E,  spinal  nerve  attached  to  spinal  cord.  Red  indicates  motor  and  blue  tensor 
impulses. 


both  varieties  of  reflex  action  the  cerebral  cortex  is  not  brought 
into  the  action. 

The  neurons  involved  in  the  movements  of  the  involuntary  muscu- 
lature of  the  body  and  secretions  of  glands  are  complicated  by  con- 
nection with  the  sympathetic  system. 

Optic  Pathway  (Fig.  305). — The  axones  of  the  first  neuron  arise 
from  the  inner  ganglion  cells  of  the  retina  and  form  the  optic  nerve; 
at  the  chiasm  those  fibers  from  the  temporal  half  of  the  retina  con- 
tinue on  the  same  side  and  those  from  the  nasal  half  cross  to  the  oppo- 
site side  through  the  chiasm.  These  crossed  and  uncrossed  fibers  of 
each  side  form  the  optic  tracts  that  curve  over  the  ventral  surface  of 
each  cerebral  peduncle  to  end  as  follows:  (1)  in  the  pulvinar  of  the 
thalamus;  (2)  in  the  lateral  geniculate  body;  (3)  a  few  fibers  pass  to 


THE    GUSTATORY    PATHWAY 


421 


the  superior  quadrigeminal  body  (eye  muscle  movements).  The 
axones  of  the  second  neurons  start  from  the  pulvinar  and  lateral  gen- 
iculate body,  form  the  optic  radiation  at  the  caudal  and  most  ven- 
tral part  of  the  internal  capsule  and  end  in  the  occipital  cortex  (visual 
area). 

The  neuron  that  ends  in  the  superior  quadrigeminal  body  is  con- 
cerned in  the  action  of  the  sphincter  pupilte  muscle  of  the  iris;  it  is 


Fig.  305. — Diagram  of  the  optic  pathway. 

succeeded  by  a  second  neuron  that  connects  the  superior  quadrige- 
minal body  with  the  nucleus  of  the  oculomotor  nerve.  A  third 
neuron  connects  this  nucleus  with  the  ciliary  ganglion  and  a,  fourth 
neuron  connects  this  ganglion  with  the  sphincter  pupillae  muscle. 

Gustatory  Pathway. — This  pathway  comprises  two  nerves,  the 
nervi  intermedins  and  the  glossopharyngens.  The  first  neuron  cell  of 
the  nervi  intermedins  lies  in  the  geniculate  ganglion  (of  the  facial 
nerve,  so  called)  and  the  peripheral  fiber  (dendrite)  ends  within  the 
tongue;  the  central  fiber  (axone)  ends  in  the  nucleus  solitarius  of  the 


422 


THE    NERVE    SYSTEM 


Fig.   306. — A  diagram  of  the  probable  pathways  of  gustatory  impulses. 


RESTBODY 


vC 


I  .       JJCI 

r 


DE/TERS 
NUC. 


tlEDNUC. 


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WRQOT  1        ■ 

MEO.      ££M. 


Fig.  307. — Diagram  of  the  nuclei  of  termination  of  the  vestibular  nerve,  and  their  higher 
connections. 


THE    AUDITORY    PATHWAY 


423 


glossopharyngeal  and  vagal  nerves.  The  first  neuron  of  the  glosso- 
pharyngeal nerve  lies  in  the  ganglia  jugulare  and  nodosum  and  the 
peripheral  fiber  (dendrite)  ends  in  the  tongue;  the  central  fiber 
(axone)  ends  in  the  nucleus  solitarius  of  the  oblongata  (as  in  the  pre- 
ceding). The  second  neuron  lies  in  this  nucleus  and  the  axon  ends  in 
the  thalamus.  The  third  neuron  starts  in  the  thalamus  and  ends  in 
the  gustatory  area  of  the  temporal  lobe  of  the  cerebral  cortex  (medial 
surface). 

Auditory  Pathway. — The  auditory  nerve  consists  of  the  cochlear 
and  vestibular  divisions.  The  first  neuron  cells  of  the  cochlear  nerve 
lie  in  the  ganglion  spirale  of  the  organ  of  Corti.     The  peripheral  fibers 


Fig.   308. — Diagram   of   the   cochle 


clei  of  terminate 


nd   their  higher  connection 


(dendrites)  end  in  relation  with  the  hair  cells  of  the  organ  of  Corti 
while  the  central  fibers  (axones)  pass  to  the  dorsal  and  ventral  coch- 
lear nuclei  of  the  oblongata  (floor  of  the  fourth  ventricle).  The 
second  neuron  cells  lie  in  these  nuclei;  the  axones  from  the  dorsal 
cochlear  nucleus  pass  over  the  floor  of  the  ventricle  (as  the  acoustic 
stria?)  to  the  median  sulcus,  then  pass  ventrally  into  the  oblongata 
cross  the  midline  and  most  of  the  fibers  pass  obliquely  to  join  the 
lateral  lemniscus  to  end  in  the  medial  geniculate  body. 

The  fibers  from  the  ventral  cochlear  nucleus  pass  toward  the  mid- 
line, just  dorsal  to  the  pyramids,  and  form  here  the  trapezium. 
They  continue  across  the  midline  and  sweep  dorsally  to  join  the 
lateral  lemniscus  and  end  in  the  medial  geniculate  body  and  the 
inferior  quadrigeminal  body.  Fibers  pass  to  and  end  in  the  superior 
olivary  nucleus.  Some  fibers  end  in  the  nucleus  of  the  lateral  lem- 
niscus and  are  replaced  by  new  fibers.  Others  may  end  in  the 
nucleus  of  the  trapezium  to  be  succeeded  by  new  fibers  from  the 
cells  here. 


424  THE    NERVE    SYSTEM 

The  third  natron  cells  lie  in  the  medial  geniculate  body  and  their 
axones  then  pass  to  the  auditory  center  which  is  in  the  superior 
portion  of  the  cortex  of  the  temporal  lobe. 

The  first  neuron  cells  of  the  vestibular  nerve  (the  nerve  of  equilibra- 
tion) lie  in  the  vestibular  ganglion  in  the  internal  auditory  canal. 
The  peripheral  fibers  (dendrites)  end  in  the  neuroepithelial  areas  of 
the  utriculus,  sacculus  and  semicircular  canals  of  the  internal  ear. 
The  central  fibers  (axones)  pass  to  the  brain  stem  where  they  divide 
into  ascending  and  descending  branches.  These  branches  end  in  the 
various  vestibular  nuclei.  The  second  neuron  cells  lie  in  these  nuclei 
and  the  axones  of  these  cells  pass  to  the  vermis  of  the  cerebellum,  to 
the  nucleus  fastigii  of  the  cerebellum,  to  the  various  cerebral  nerve 
nuclei  through  the  median  longitudinal  fasciculus  (from  Deiter's 
nucleus),  to  the  superior  olive,  to  the  spinal  cord  (through  the  ves- 
tibulospinal tract)  and  possibly  to  the  thalamus.  Third  to  cortex. 
Pathway  for  Touch,  Temperature  and  Pain. — In  the  trunk  and 
extremities,  the  first  neuron  cells  lie  in  the  ganglia  of  the  dorsal  roots 
of  the  spinal  nerves.  The  peripheral  fibers  (dendrites)  bring  the 
impulses  from  the  periphery  (organ  or  skin)  and  it  is  then  conveyed 
by  the  axone  into  the  spinal  cord  through  the  dorsal  root;  the  axones 
end  in  the  gray  substance  of  the  dorsal  horn.  The  second  neuron  cells 
lie  here  and  their  axones  cross  through  the  ventral  gray  commissure 
to  the  opposite  side  and  form  the  spinothalamic  tracts  in  the  spinal 
cord  and  in  the  oblongata  they  join  the  medial  lemniscus  to  end  in 
the  thalamus.  The  third  neuron  cells  lie  in  the  thalamus  and  the 
axones  pass  through  the  internal  capsule  (sensor  limb)  to  the  cortical 
area  of  somatic  sensibility  (postcentral  gyre).  Some  of  the  impulses 
of  touch  and  contact  sensibility  are  conveyed  through  the  dorsal 
column  of  the  spinal  cord  (same  side)  to  the  nucleus  cuneatus  and 
gracilis.  The  new  fibers  from  these  nuclei  decussate  and  join  the 
opposite  medial  lemniscus  to  end  in  the  thalamus  of  that  side;  thus 
some  of  the  sensibility  fibers  cross  in  the  spinal  cord  at  their  entrance 
and  others  do  not  cross  until  the  above  nuclei  have  been  reached. 

In  the  head  most  of  the  impulses  are  conducted  to  the  nuclei  of 
the  trigeminus,  glossopharyngeal  and  vagal  nerves  of  each  side  to 
the  ganglia  of  the  sensor  divisions;  then  they  are  conducted  to  the 
nuclei  of  termination  of  these  nerves,  in  the  fourth  ventricle.  This 
course  constitutes  the  first  neuron.  The  second  neurons  connect 
these  nuclei  with  the  thalamus  by  way  of  the  medial  lemniscus.  The 
third  neurons  connect  the  thalamus  with  the  cerebral  cortex  as  above. 

The  muscle  sense  (deep  sensibility)  impulses  of  the  trunk  and 
extremities  are  conveyed  as  follows:  The  first  natron  connects  the 
periphery  with  the  spinal  cord  where  some  of  the  fibers  continue 
on  the  same  side  through  the  dorsal  column  to  the  nuclei  cuneatus 
and  gracilis.     From  here  the  fibers  of  the  second  neuron  convey  the 


TRACTS    CONCERNED    IN    RESPIRATION 


425 


impulses  by  way  of  the  opposite  medial  lemniscus  to  the  thalamus. 
The  third  neuron  connects  the  thalamus  with  the  cortical  area. 
Some  fibers  pass  from  the  nuclei  gracilis  and  cuneatus  to  the  cere- 
bellar cortex;  new  fibers  pass  from  here  to  the  dentate  nucleus  of 
the  cerebellum  from  which  new  fibers  pass  to  the  thalamus  through 
the  brachia  conjunctiva. 

Some  of  the  fibers,  only,  of  the  first  neuron,  have  the  above  course. 
Others,  after  entering  the  dorsal  roots  of  the  spinal  nerves,  do  not 
enter  the  dorsal  column  but  join  the  spinocerebellar  tracts  (ventral 
and  dorsal  superficial)  to  end  in  the  cerebellar  cortex  of  the 
same  side.  The  impulses  are  then  carried  to  the  dentate  nucleus 
and  from  here  through  the  brachium  conjunctivum  to  the  thalamus; 
from  the  thalamus  the  impulses  are  conveyed  to  the  cerebral  cortex. 


Fig.  309. — Diagn 


;  and  tracts  concerned  in  respiration. 


Respiration. — Although  respiration  is  apparently  controlled  by 
the  respiratory  nucleus  that  lies  in  the  formatio  reticularis  of  the 
oblongata,  it  is  maintained  by  stimuli  carried  to  this  center  by  the 
blood  vascular  system  and  reflex  impulses  from  the  sensor  portion 
of  the  vagus  through  cells  in  the  nucleus  of  termination  of  the  vagal 
nerve  and  by  impulses  from  the  higher  respiratory  centers.  The 
respiratory  nucleus  is  connected  with  the  following  motor  nuclei: 
Facial,  vagal,  accessory,  cervical  plexus,  phrenic,  brachial  plexus 
and  thoracic  nerves.     Axones  from  the  higher  centers  and  from  the 


426 


THE    NERVE    SYSTEM 


sensor  vagal  nucleus  end  in  the  respiratory  nucleus.  The  cells  of  the 
respiratory  nucleus  send  their  axones  directly,  or  by  means  of  col- 
laterals, in  the  formatio  reticularis,  to  the  nuclei  of  the  above- 
mentioned  motor  nerves  so  that  through  this  connection  a  number 
of  cerebral  and  spinal  nerves  are  caused  to  act. 

Olfactory  Nerves  and  Pathway. — Each  so-called  olfactory  nerve 
consists  of  about  twelve  separate  nerves  called  the  olfactory  fila.  These 
arise  in  the  olfactory  mucosa  of  the  nose,  pass  through  the  openings 
in  the  cribriform  plate  of  the  ethmoid  bone  and  terminate  in  the 
olfactory  bulb. 


Medial  stria. 

Lateral  stria. 

Inlermedictte  sit 


Bulb 

Tract 

Trigone 

Gyrus  ambiens 

Gyrus  semilunaris- 

Uncus 


-Schematic  representation  of  the  olfactory  pathway  upon  the  ' 
the  brain. 


ntral  surface  of 


The  olfactory  path-way  comprises  the  olfactory  fila  and  the  rhinen- 
cephalon,  the  parts  of  which  will  be  considered  under  peripheral  and 
central,  or  cortical  portions. 

The  peripheral  portion  comprises  the  following: 

The  olfactory  bulb  (biilbus  olfactorius)  that  receives  the  olfactory 
fila.  Each  lies  upon  the  cribriform  plate  of  the  ethmoid  bone.  It 
is  oval  in  outline,  flattened  and  of  a  reddish  color.  It  is  continued 
toward  the  cerebrum  as  the  olfactory  tract. 

The  olfactory  tract  (tractits  olfactorius)  is  a  wedge-shaped  band  of 
nerve  fibers  and  passes  from  the  bulb  toward  the  cerebrum.  After 
a  course  of  about  3.5  cm.  it  forms  the  olfactory  tubercle  {tuberculiim 
olfactorium)  the  base  of  which  is  seen  in  the  ventral  surface  of  this 
region  and  is  called  the  trigonum  olfactorium  (gray  nerve  tissue). 

From  the  trigonum  three  tracts,  or  striae,  continue,  called  the  lateral, 


THE    OLFACTORY    PATHWAY  427 

intermediate  and  medial  roots,  or  stria,  of  which  each  has  a  different 
course  and  termination.  Each  lateral  root  (stria  olfacloria  lateralis) 
passes  to  the  sylvian  fissure  where  it  is  continuous  with  the  limen 
insula  and  then  continues  to  the  gyri  ambiens  and  semilunaris. 

The  intermediate  root  (stria  olfacloria  intermedins)  extends  from 
the  olfactory  tract  over  the  trigonum  to  the  gray  substance  of  the 
anterior  perforated  substance. 

The  medial  root  (stria  olfacloria  medialis)  passes  to  and  merges 
with  the  area  parolfactoria. 

Broca's  diagonal  band  is  seen  ventrally  in  the  anterior  perforated 
space.  This  comes  from  the  uncus  and  courses  obliquely  along  the 
outer  side  of  the  optic  tract,  converging  with  its  fellow  of  the  oppo- 
site side  to  the  base  of  the  intercerebral  cleft  where  they  pass  dor- 
sally  into  the  gyrus  subcallosus  under  the  genu  of  the  corpus  callosum. 
From  here  each  continues  in  the  indusium  of  that  side  forming  the 
medial  and  lateral  longitudinal  stria?. 

The  anterior  perforated  substance  lies  just  behind  (caudad  of)  the 
trigonum  between  this  and  the  optic  chiasm.  It  is  somewhat  quad- 
rilateral in  shape.  In  the  lateral  and  caudal  part  of  this  area  is 
Broca's  diagonal  line. 

The  area  parolfactoria  lies  in  the  base  of  the  intercerebral  cleft 
under  the  genu  of  the  corpus  callosum. 

The  gyrus  ambiens  and  gyrus  semilunaris  are  seen  upon  the  ventral 
surface  to  the  side  of  the  corpora  albicantia,  bounding  the  anterior 
perforated  space  caudolaterally.  They  represent,  apparently,  a 
portion  of  the  uncus  separated  therefrom  by  the  end  of  the  dentate 
gyre,  called  the.  frenulum  Giacomini.  They  are  a  part  of  the  hippo- 
campal  gyre. 

The  central  portions  are  sometimes  called  the  limbic  lobe  and  are 
as  follows: 

The  gyrus  subcallosum  lies  just  behind  the  area  parolfactoria 
under  the  genu  of  the  corpus  callosum  continuing  as  the  indusium. 

The  indusium  (gyrus  epicallosus)  is  a  thin  band  of  gray  nerve 
tissue  extending  over  the  dorsal  surface  of  the  corpus  callosum. 
Through  it  ran  the  medial  and  lateral  longitudinal  stria;,  or  roots, 
forming  two  ridges.  The  indusium  continues  ventrally  as  the  gyrus 
dentatus.  The  medial  and  lateral  longitudinal  stria  are  continuations 
of  Broca's  diagonal  band. 

The  hippocampus  is  a  portion  of  the  temporal  lobe  that  projects 
into  the  middle  horn  of  the  lateral  ventricle.  Upon  it  lies  a  white 
band,  the  fimbria,  a  portion  of  the  fornix. 

The  uncus  is  a  hook-like,  isolated  portion  of  the  hippocampal 
gyre  just  behind  the  gyrus  ambiens  upon  the  ventral  surface  of  the 
brain  just  lateral  to  the  frontal  portion  of  the  pons. 

The  dentate  gyre  is  a  notched  band  of  gray  nerve  tissue  in  the 


428 


TlIK    MO  RYE    SYSTEM 


depths  of  the  hippochampal  fissure  that  separates  it  from  the  hippo- 
campal  gYre.  On  the  other  side  is  a  fissure  that  separates  it  from 
the  fimbria,  in  the  depths  of  which  is  a  narrow  band,  the  fasciola 
cinerca;  this  is  a  narrow  extension  of  the  uncus  to  the  splenial  portion 
of  the  callosum,  where  it  fuses  with  the  dentate  gyre.  The  dentate 
gyre  seems  to  be  a  continuation  of  the  indusium  that  extends  ven- 
trally  around  the  uncus  as  the  frenulum  Giacomini. 

The  gyrus  Andres  Retzii  is  a  small,  oval,  corrugated  portion  of  the 
hippochampal  gyre  just  behind  the  splenium  of  the  corpus  callosum. 

The  corpora  albicantia  are  two,  small,  rounded,  white  structures, 
on  the  ventral  surface  of  the  brain  just  caudad  of  the  optic  chiasm 


Sub  calhsal  ay> 
^rea  parolfactory 


'Frenulum  GicLcommi . 
Tra.ci' lntesmea'>aJ*\'_f         '      Frenulum  gyrus  arnbienS 
jtrta.        j   .      Gyrvs  semilunaris. 


-Schematic  representation  of  the  olfactory  pathway. 


(intercrural  space)  and  near  the  midline.  Their  white  color  is  due 
to  the  myelinated  nerve  fibers  of  the  fornix  that  end  here  in  the 
central  gray  nerve  tissue.  This  gray  tissue  is  usually  arranged  as 
two  nuclear  masses  in  each  body. 

The  anterior  commissure  is  seen  in  the  frontal  wall  of  the  third 
ventricle,  as  it  courses  from  side  to  side.  It  is  usually  a  small  bundle 
of  nerve  fibers  of  which  the  frontal  portion  belongs  to  the  olfactory 
pathway.  It  connects  the  uncus  of  the  two  sides  with  each  other  in 
addition  to  containing  the  pathway  fibers  from  the  bulb. 

The  septum  pellucidum  consists  of  two  layers  enclosing  a  portion  of 
the  early  intercerebral  cleft,  during  the  formation  of  the  callosum. 
This  space  is  the  so-called  fifth  ventricle  but  is  not  a  part  of  the  true 
ventricular  system  of  the  brain.  The  septum  is  enclosed  in  the  arch 
of  the  corpus  callosum  and  extends  from  it  to  the  fornix.  Its  frontal 
part  contains  some  gray  nerve  tissue  that  is  a  part  of  the  olfactory 
pathway.     Occasionally  an  opening  is  seen  in  the  septum  permitting 


THE    OLFACTORY    PATHWAY  429 

communication  between  the  two  lateral  ventricles.  Also,  in  two 
instances  the  writer  has  noticed  that  the  septum  extended  all  the  way 
from  the  genu  to  the  splenium  and  w^as  twice  as  long  as  in  the  usual 
specimens. 

The  fornix  is  a  paired  structure  consisting  of  longitudinally  cours- 
ing fibers  connecting  the  uncus  and  corpus  albicans  of  each  side. 
It  consists  of  a  body  and  a  pair  of  anterior  (frontal)  and  a  pair  of  pos- 
terior (occipital)  pillars.  The  body  is  that  portion  ventral  of  the 
body  of  the  callosum  where  the  two  tracts  lie  side  by  side.  Fron- 
tally,  at  the  region  of  the  anterior  commissure,  the  two  tracts  diverge 
and  course  ventrally,  as  the  anterior  pillars,  to  end  in  the  corpus 
albicans  of  each  side.  Occipitally,  at  the  splenium  of  the  callosum, 
these  tracts  diverge  as  the  posterior  pillars  and  pass  first  ventrally  and 
then  frontally  in  a  hook-like  manner  to  end  in  the  uncus  of  each  side. 
As  the  pillars  pass  ventrally  they  project  into  the  inferior  (temporal) 
horn  of  the  lateral  ventricle  and  lie  upon  the  hippocampus,  here 
constituting  a  band  of  fibers  called  the  fimbria;  this  dwindles  in  size 
as  the  uncus  is  approached. 

Impulses  arising  in  the  olfactory  portion  of  the  nasal  mucosa  pass 
to  the  olfactory  bulb  by  way  of  the  olfactory  fila.  This  constitutes 
the  peripheral  tract  (first  neuron).  From  the  bulb  the  impulses  are 
conducted  by  another  neuron  system,  by  way  of  the  olfactory  tract, 
to  the  primary  centers,  i.e.,  the  gray  substance  of  the  tractus  olfactor- 
ium,  trigonum,  anterior  perforated  substance  and  the  gray  substance 
of  the  septum  lucidum.  The  impulses  are  then  conducted  to  the  cor- 
tical centers  by  a  third  neuron. 

The  lateral  olfactory  stria  carries  the  impulses  to  the  gyrus  ambiens 
and  gyrus  semilunaris  from  the  trigonum.  The  intermediate  stria 
carries  the  impulses  to  the  gray  substance  of  the  anterior  perforated 
space;  from  the  trigonum,  the  anterior  perforated  substance  and  the 
septum  lucidum  impulses  pass  to  the  hippocampus  by  way  of  the 
fornix. 

The  medial  olfactory  stria  consists  of  fibers  from  the  trigonum  that 
pass  toward  the  gyrus  subcallosus  and  then  over  the  corpus  callosum 
through  the  dentate  gyre  to  end  in  the  hippocampus. 

Other  fibers  pass  from  the  anterior  perforated  substance  and  the 
septum  pellucidum  to  the  nucleus  amygdala  and  the  thalamus. 

The  hippochampus  is  connected  with  the  corpus  albicans  of  each 
side  by  the  fornix  fibers  that  arise  from  the  cells  of  the  hippocampus 
and  the  dentate  gyre.  As  the  fornix  passes  ventral  to  the  corpus 
callosum  it  receives  fibers  from  the  medial  longitudinal  stria3,  dorsal 
to  the  callosum,  that  pass  to  this  body  and  constitute  the  fibres 
perforantcs.  While  most  of  the  fornix  fibers  pass  to  the  corpus  albi- 
cans some  pass  to  the  ganglion  habenula  (a  small  nucleus  between  the 
epiphysis  and  the  caudal  end  of  the  thalamus). 


43° 


THE    NERVE    SYSTEM 


The  corpus  albicans  of  each  side  is  further  connected  with  the  thal- 
amus and  the  tegmentum  of  the  crus  cerebri,  where  there  is  a  small 
ganglion,  the  ganglion  pro/ionium  tegmcnti. 

THE  CIRCULATION  OF  THE  BRAIN 

The  arteries  (Fig.  312)  that  supply  the  brain  are  the  two  vertebral 
(arteries  vertebrates)  and  the  two  internal  carotid  arteries  (arteries 
carol  ides  internee).     The  latter  enter  the  cranial  cavity  through  the 


Olfactory  bulb 


SG^neri/e 

Int.  carotid  artery 
^nerve 


Vertebral  art. 

Spmat  cord  \         ^\^t'n  f.  Cere6e//*r  art 
Fig.  312. — The  arteries  of  the  base  of  the  brain.     (After  Sobotta  and  McMurrich.) 

carotid  canals  while  the  former  enter  through  the  foramen  magnum. 
The  vertebral  arteries  join  to  form  the  basilar  artery  (arteria  basilaris) 
the  largest  branches  of  which  are  the  two  posterior  cerebral  arteries 
(arteria;  cerebri  posteriores) .  The  internal  carotid  arteries  give  rise 
to  a  branch,  the  posterior  communicating  artery,  that  passes  back 
and  anastomoses  with  the  posterior  cerebral  artery  on  each  side. 
In  front  each  internal  carotid  artery  gives  rise  to  an  anterior  cerebral 
artery  (arteria  cerebri  anterior)  which  is  connected  to  its  fellow  on  the 
opposite  side  across  the  midline  by  the  anterior  communicating 
artery.  Thus  a  so-called  circle  is  formed  at  the  base  of  the  brain 
called  the  circle  of  Willis  (circulus  adenosis). 


VEINS  431 

The  other  branches  of  each  vertebral  artery  are  the  following: 
The  posterior  meningeal. 

The  ventral  spinal,  one  on  each  side,  which  unite  to  form  a  single 
vessel  that  lies  at  the  front  of  the  ventral  median  fissure  of 
the  spinal  cord. 
The  dorsal  spinal  artery,  one  descending  upon  each  side  behind 

the  dorsal  roots  of  the  spinal  nerves. 
The  posterior  inferior  cerebellar. 
Bulbar. 
The  basilar  artery  gives  the  following  branches: 
Internal  auditory. 
Anterior  inferior  cerebellar. 
Superior  cerebellar. 
Posterior  cerebral. 
The  internal  carotid  gives  rise  to  the  following  branches: 
Posterior  communicating. 
Middle  cerebral  (in  the  sylvian  fissure). 

The  anterior  cerebral  that  winds  over  the  callosum  and  lies  in 
the  longitudinal  fissure. 
The  central  ganglionic  masses  are  supplied  by  branches  of  the  circle 
of  Willis,  or  trunks  close  to  it. 

Veins. — The  blood  is  returned  from  the  cerebrum  by  the  super- 
ficial and  the  deep  cerebral  veins  {vena?  cerebri).  The  superficial  veins 
receive  the  blood  from  the  convolutions  and  deeper  parts  and  empty 
into  the  sinuses.  The  deep  veins,  or  internal  cerebral  veins  (Galen) 
unite  to  form  a  short  trunk,  the  vena  magna  Galeni,  that  ends  in  the 
straight  sinus. 

The  blood  from  the  cerebellum  is  returned  by  the  superficial  and 
deep  cerebellar  veins  which  return  the  blood  to  the  transverse,  superior 
and  inferior  petrosal  and  the  occipital  sinuses. 

The  blood  from  the  pons  is  returned  to  the  cerebellar  veins,  or  the 
superior  petrosal  sinus. 

From  the  oblongata  the  blood  is  returned  to  the  inferior  petrosal 
sinus,  or  the  basilar  plexus. 

The  sinuses  in  the  dura  that  receive  the  blood  from  the  brain  are 
the  following: 
Single: 

Superior  sagittal  sinus. 
Inferior  sagittal  sinus. 
Straight  sinus. 
Occipital  sinus. 
Circular  sinus. 
Basilar  sinus. 
Paired: 
Lateral  sinuses. 


432  THE    NERVE    SYSTEM 

Sphenoparietal  sinuses. 
Superior  petrosal  sinuses. 
Inferior  petrosal. 
Cavernous. 

The  superior  sagittal  sinus  (si)nis  sagittalis  superior)  lies  in  the  up- 
per edge  of  the  falx  cerebri  and  extends  from  the  foramen  cecum,  in 
front,  to  the  torcular  Herophili  (confluens  sinuum),  behind. 

The  inferior  sagittal  sinus  {sinus  sagittalis  inferior)  lies  in  the 
lower  edge  of  the  falx  cerebri  and  extends  backward  to  the  frontal 
edge  of  the  tentorium  cerebelli  to  end  by  joining  the  deep  cerebral 
vein  (Galen)  to  form  the  straight  sinus. 

The  straight  sinus  (sinus  rectus)  extends  along  the  upper  surface 
of  the  tentorium  cerebelli,  from  the  end  of  the  inferior  sagittal  sinus 
to  the  torcular  Herophili. 

The  occipital  sinus,  the  smallest,  is  formed  from  veins  around  the 
margin  of  the  foramen  magnum  and  terminates  in  the  torcular 
Herophili. 

The  circular  sinus  (anterior  and  posterior  intercavernous  sinuses) 
is  situated  in  the  pituitary  fossa  and  surrounds  the  pituitary  body 
and  is  connected  on  each  side  with  the  cavernous  sinus. 

The  basilar  sinus  (plexus  basilaris)  extends  across  the  basilar  por- 
tion of  the  occipital  bone  and  connects  the  ends  of  the  cavernous, 
or  the  ends  of  the  superior  petrosal  sinuses  to  each  other. 

The  lateral  sinuses  (sinus  transversi)  begin  at  the  torcular  and 
pass  outward  and  then  downward  to  the  jugular  foramen  of  the  skull; 
here  each  ends  in  the  internal  jugular  vein  of  that  side.  They  are 
the  largest  sinuses  and  carry  most  of  the  blood  out  of  the  skull. 

The  sphenoparietal  sinuses  (sinus  sphenoparietalcs)  lie  under  the 
lesser  wings  of  the  sphenoid  bone  and  each  terminates  in  the  ante- 
rior end  of  the  corresponding  cavernous  sinus. 

The  cavernous  sinus  (sinus  cavemosi)  lie  upon  the  side  of  the 
body  of  the  sphenoid  bone  and  extend  from  the  sphenoidal  fissure 
to  the  apex  of  the  petrous  portion  of  the  temporal  bone.  These 
communicate  with  each  other  through  the  circular  sinus  and  receive 
the  blood  from  the  sphenoparietal  sinuses  and  send  the  blood  into 
the  superior  and  inferior  petrosal  sinuses. 

The  superior  petrosal  sinuses  (sinus  petrosi  superiores)  start  at 
the  same  regions,  pass  downward  and  outward  along  the  lower 
margin  of  the  petrous  portion  of  the  temporal  bone;  each  ends  in 
the  lateral  sinus  of  that  side. 

The  inferior  petrosal  sinuses  (sinus  petrosi  inferiores)  begin  at 
the  posterior  end  of  the  cavernous  sinus  of  each  side  and  pass  down- 
ward, backward  and  laterally  in  the  posterior  fossa  of  the  skull  and 
empty  into  the  internal  jugular  vein  of  that  side. 

The  veins  of  the  spinal  cord  form  a  plexus  in  the  pia  and  from  this 


THE    CEREBRAL    NERVES  433 

plexus  six  main  longitudinal  and  radicular  veins  are  formed.  The 
longitudinal  veins  are  one  ventromedial!,  two  ventrolateral,  two  dorso- 
lateral and  one  dorsomedian. 

The  radicular  veins  pass  around  the  nerve  roots  to  terminate  in 
the  ventral  and  dorsal  spinal  "veins. 

The  venlromedian  and  dorsomedian  veins  empty  into  veins  of  the 
oblongata;  the  lateral  veins  empty  partly  into  the  preceding  but 
chiefly  into  the  two  radicular  veins  that  carry  their  blood  to  the 
ventral  and  dorsal  spinal  veins  of  the  vertebral  column. 

The  intracranial  lymphatics  are  meningeal  and  cerebral.  The 
meningeal  lymphatics  start  in  the  spaces  of  the  dura,  follow  the 
blood-vessels  and  empty  into  the  internal  maxillary  and  upper  deep 
cervical  lymph  nodes. 

The  Peripheral  Nerve  System 

The  peripheral  nerve  system  comprises  the  cerebral  and  spinal 
nerves  and  their  associated  ganglia. 

THE  CEREBRAL  OR  ENCEPHALIC  NERVES 
The  term  cerebral  nerves  is  poorly  chosen  as  the  first  two  pairs, 
only,  are  connected  with  the  cerebrum  and  these  are  not  considered 
true  nerves  but  outgrowths  of  the  cerebral  vesicles;  the  others 
are  connected  with  the  brain  stem.  The  term  encephalic  nerves 
would  be  more  satisfactory  as  the  distinction  from  spinal  nerves  would 
be  maintained  and  the  origin  from  the  brain,  as  a  whole,  would 
be  expressed. 

The  cerebral  nerves  are  twelve  pairs  in  number  and  ten  pairs  are 
directly  connected  with  the  brain  stem  in  which  lie  their  nuclei  of 
origin,  or  termination.     These  nerves  vary,  some  are  purely  motor, 
others  purely  sensor  (special  senses)  and  others  are  mixed. 
These  nerves  are  classified  as  follows: 
i.  Olfactory.     Pure  sensor,  special  sense  (smell). 

2.  Optic.     Pure  sensor,  special  sense  (vision). 

3.  Oculomotor.     Pure  motor. 

4.  Trochlear.     Pure  motor. 

5.  Trigeminus.     Mixed. 

6.  Abducens.     Pure  motor. 

7.  Facial.     Mixed.     Special  sense  (taste). 

8.  Auditory.     Pure  sensor,  special  sense  (hearing). 

9.  Glossopharyngeal.    Mixed.     General  and  special  sense  (taste). 
10.  Vagus.     Mixed. 

n.  Spinal  accessory.     Pure  motor. 
12.  Hypoglossal.     Pure  motor. 

For  the  sake  of  convenience  these  will  be  taken  up  in  reverse  order 
just  as  the  brain  was  considered  from  the  oblongata  to  the  cerebrum. 


434 


THE    XERYE    SYSTEM 


Hypoglossal  Nerve  (Nervus  Hypoglossus). — This  is  the  motor 
nerve  of  the  tongue  and  its  nucleus  lies  in  the  lower,  or  caudal  end 
of  the  gray  substance  of  the  fourth  ventricle.  This  nucleus  is  about 
18  mm.  long  and  quite  narrow;  it  extends  from  the  upper  level  of  the 
pyramidal  decussation  to  the  stria;  acusticae  and  close  to  the  mid- 
line. It  represents  a  continuation  of  the  motor  gray  of  the  spinal 
cord.     The  upper  end  of  the  nucleus  lies  beneath  the  trigonum 


Fig.  313. — The  hypoglossal 


and  distribution. 


hypoglossi  of  the  fourth  ventricle.  The  two  nuclei  are  connected 
across  the  midline  by  commissural  fibers  and  fibers  from  the  opposite 
pyramid  end  in  each  nucleus,  completing  thus  the  connection  with 
the  cerebral  cortex.  The  nerve  cells  are  large  and  their  myelinated 
axis-cylinders  pass  ventrally  through  the  formatio  reticularis,  be- 
tween the  olivary  nucleus  and  the  pyramid,  to  emerge  (superficial 
origin)  in  the  groove  between  these  two  structures  on  the  ventral 
surface  of  the  oblongata. 


THE    ACCESSORY    NERVE  435 

The  hypoglossal  nerve  leaves  the  cranial  cavity  through  the  hypo- 
glossal canal,  enters  the  neck,  passes  downward,  ventrally  and  medi- 
ally to  the  tongue.  It  gives  off  the  recurrent,  descending,  thyreo- 
hyoid  and  lingual  branches. 

The  recurrent  branch  (ramus  rccurrens)  is  given  off  in  the  cranial 
cavity  and  supplies  the  dura  of  the  posterior  fossa.  The  descending 
branch  (ramus  descendens)  forms  the  hypoglossal  loop  with  a  branch 
from  the  second  and  third  cervical  nerves  and  supplies  the  mm. 
omohyoideus,  sternohyoideus  and  sternothyreoideus.  The  thyreoid 
branch  (ramus  thyreoidens)  supplies  the  m.  thyreohyoideus.  The 
lingual  branches  (rami  lingualcs)  supply  the  mm.  hyoglossus, 
genioglossus,  geniohyoideus  and  the  intrinsic  muscles  of  the  tongue. 

The  hypoglossal  nerve  communicates  with  the  superior  cervical 
ganglion  (sympathetic),  the  ganglion  nodosum  of  the  vagal  nerve, 
the  upper  cervical  nerves,  the  pharyngeal  plexus  and  the  lingual 
branch  of  the  mandibular  nerve  (trigeminal). 

The  Spinal  Accessory  Nerve  (Xervus  Accessories). — This  is  a  pure 
motor  nerve  consisting  of  a  spinal  division  (representing  a  spinal 
nerve)  and  an  accessory  portion  arising  from  the  oblongata  (bulbar 
part).  The  spinal  part  arises  from  the  dorsolateral  nerve  cells  in 
the  ventral  horn  of  the  first  four  cervical  segments  of  the  spinal  cord. 
These  myelinated  axones  pass  ultimately  to  the  surface  of  the  spinal 
cord,  emerge  at  the  lateral  column  and  pass  up  through  the  foramen 
magnum  to  join  the  bulbar  portion.  The  accessory,  or  bulbar  root, 
arises  from  nerve  cells  in  the  ventricular  gray  at  the  upper  (cephalic) 
end  of  the  spinal  nucleus  and  is  practically  a  continuation  of  the 
lower,  or  caudal  end  of  the  nucleus  ambiguus  of  the  vagal  and  glosso- 
pharyngeal nerves.  It  is  lateral  to  the  lower  end  of  the  hypoglossal 
nucleus  and  is  called  the  nidus  laryngci,  because  its  fibers  later  join 
the  vagus  and  though  this  nerve  pass  to  the  intrinsic  muscles  of  the 
larynx,  except  the  cricothyreoid  muscle.  The  spinal  root  supplies 
the  trapezius  and  sternomastoid  muscles. 

Fibers  from  the  opposite  pyramids  end  in  each  nucleus  (cortical 
connections)  as  do  also  fibers  from  the  dorsal  (sensor)  roots  of  the 
spinal  nerves  (establishing  a  reflex  arc). 

The  superficial  origin  of  the  bulbar  portion  of  the  accessory  nerve 
is  the  side  of  the  oblongata,  at  the  head  end  of  the  restiform  body. 
The  spinal  portion  arises  from  the  side  of  the  spinal  cord  as  low  as 
the  sixth  cervical  nerves.  These  two  portions  join  and  leave  the 
cranial  cavity  through  the  jugular  foramen.  The  bulbar  root  sends 
a  branch  to  the  ganglion  nodosum  of  the  vagal  nerve  and  the  re- 
mainder joins  the  vagal  nerve  and  ultimately  supplies  the  intrinsic 
muscles  of  the  larynx  (except  the  m.  cricothyreoideus),  and  furnishes 
cardioinhibitory  nerves  to  the  vagus.  The  spinal  portion  (ramus 
extcrnus)  passes  into  the  neck  and  supplies  the  mm.  sternomastoideus 
and  trapezius. 


436  THE    NERVE    SYSTEM 

The  spinal  portion  communicates  with  the  cervical  plexus. 

Vagal  and  Glossopharyngeal  Nerves  (Nervus  Vagus  et  Nervus 
Glossopharyngeus) . — These  nerves,  though  mixed,  are  mainly  sensor 
and  as  their  nuclei  of  origin  and  termination  are  so  close  together  and 
so  intimately  associated  they  will  be  considered  together.     It  is 


highly  probable  that  the  glossopharyngeal  nerve  is  purely  sensor. 
The  nuclei  are  the  dorsal  (mixed)  nucleus,  nucleus  ambiguus  and 
nucleus  of  the  fasciculus  solitarius. 

The  dorsal  {mixed)  nucleus,  long  and  rod-shaped,  lies  at  the  upper 
end  of  the  hypoglossal  nucleus  and  the  motor  part  comprises  that 
portion  nearest  the  midline.     The  axones  of  the  cells  in  this  portion 


THE    VAGAL    AND    GLOSSOPHARYNGEAL    NERVES 


437 


pass  obliquely  ventrolateral  between  the  olivary  nucleus  and  the 
restiform  body,  emerging  from  the  oblongata  between  the  olive  and 
the  end  of  the  lateral  column.  The  fibers  belong  to  the  vagus  and 
pass  to  the  esophagus,  stomach,  trachea  and  bronchi.  This  is  a 
nucleus  of  origin  and  the  sensor  part  will  be  discussed  later. 

The  nucleus  ambiguus  is  deeply  placed  in  the  formatio  reticularis 
and  the  substantia  gelatinosa;  it  seems  to  be  a  continuation  of  the 
bulbar  part  of  the  accessory  nerve.  The  axones  pass  first  dorsally, 
then  bend  ventrally  and  join  the  preceding,  supplying  the  esophagus, 


-Diagram  of  the  course  of  the  trigeminal,  glossopharyngeal  and  vagal 
the  brain  stem.     Motor  nuclei  solid  black,  sensor  nuclei  dotted. 


pharynx  and  the  m.  cricothyreoideus  of  the  larynx.  Apparently  a  por- 
tion of  this  nucleus  is  cardiq-inkibitory.     This  is  also  a  nucleus  oj  origin. 

The  sensor  fibers  arise  from  cells  in  the  ganglia.  Connected  with 
the  vagus  are  the  jugular  gang! inn  (ganglion  jugulare)  and  the  gang- 
lion nodosum.  Connected  with  the  glossopharyngeus  are  the  gang- 
lion superior  and  the  ganglion  pclrosum.  These  ganglia  are  compar- 
able to  the  ganglia  connected  with  the  dorsal  (sensor)  roots  of  the 
spinal  nerves.  The  axones  of  the  cells  in  these  ganglia  enter  the 
oblongata,  branch  into  ascending  and  descending  fibers  that  ter- 
minate in  the  nucleus  ala  cinerea  and  the  nucleus  of  the  tractus  soli- 
tarius,  or  trineural  fasciculus,  respectively.  These  are  the  nuclei  of 
termination. 

The  nucleus  ala  cinerea  is  the  sensor  part  of  the  previously  men- 
tioned dorsal  nucleus  and  it  receives  ascending  branches,  above- 
mentioned;  these  are  chiefly  vagal  so  that  the  bulk  of  this  nucleus 
belongs  to  the  vagus. 


438  THE    NERVE    SYSTEM 

The  nucleus  and  Iraclus  solitarius  form  a  spindle-shaped  column  in 
the  dorsal  area  of  the  oblongata  between  the  descending  root  of  the 
trigeminal  nerve  and  the  fibers  are  mainly  of  the  glossopharyngeal 
nerve.  Only  a  few  vagal  fibers  enter  this  nucleus  and  there  are 
reasons  to  believe  that  all  of  the  glossopharyngeal  fibers  terminate 
here.  This  nucleus  and  tract  extend  from  the  upper  limit  of  ob- 
longata into  the  spinal  cord  as  far  as  the  fourth  cervical  segment. 
From  the  cells  of  all  of  these  sensor  nuclei  axones  pass  to  the  opposite 
side  of  the  oblongata,  join  the  lemniscus  and  pass  to  the  thalamus 
and  ultimately  establish  a  connection  with  the  cerebral  cortex. 

The  vagal  and  glossopharyngeal  nerves  arise  from  the  oblongata 
between  the  olivary  and  the  restiform  bodies  (superficial  origin). 
They  leave  the  cranial  cavity  through  the  jugular  foramen. 

In  the  jugular  foramen  the  vagus  has  two  ganglia,  jugular  and 
nodosum.  The  nerve  passes  through  the  neck  in  the  carotid  sheath, 
passes  through  the  thorax  and  enters  the  abdomen.  The  jugular 
ganglion  gives  off  branches  to  the  meninges  and  to  the  auricle  and 
the  external  auditory  canal.  The  ganglion  nodosum  gives  off  the 
pharyngeal  and  superior  laryngeal  nerves.  The  pharyngeal  nerve 
assists  in  forming  the  pharyngeal  plexus  that  supplies  most  of  the 
muscles  of  the  pharynx  and  soft  palate.  The  superior  laryngeal 
nerve  divides  into  external  and  internal  branches.  The  external 
branch  supplies  the  m.  cricothyreoideus.  The  internal  branch  sup- 
plies the  mucous  membrane  of  the  larynx. 

In  the  neck  the  vagus  gives  off  the  cardiac  branches,  and  recurrent 
laryngeal  nerves. 

The  superior  and  inferior  cardiac  nerves  of  the  right  side  join  the 
deep  cardiac  plexus  of  the  thorax.  The  left  superior  cardiac  nerve 
joins  the  deep  cardiac  plexus  while  the  left  inferior  cardiac  nerve 
joins  the  superficial  cardiac  plexus.  The  recurrent  laryngeal  nerve 
gives  off  muscular  branches  to  the  trachea  and  esophagus  and  then 
ends  in  the  larynx  to  supply  all  of  the  muscles  except  the  m.  crico- 
thyreoideus.    This  is  the  bulbar  portion  of  the  accessory  nerve. 

In  the  thorax  the  vagus  assist  in  forming  the  cardiac,  pulmonary 
and  coronary  plexuses.     These  are  described  on  page  470. 

In  the  abdomen  the  vagi  give  branches  to  the  stomach  and  to  the 
celiac,  splenic,  renal  and  hepatic  plexuses. 

The  glossopharyngeal  nerve  arises  just  behind  the  vagus.  As  it 
passes  through  the  jugular  foramen  it  exhibits  two  ganglia,  the 
superior  and  petrous  ganglia.  The  superior  gives  off  no  branches. 
The  petrous  ganglion  gives  off  the  tympanic  branch  that  assists  in 
forming  the  tympanic  plexus  that  supplies  the  mucosa  of  the  tym- 
panum, mastoid  cells  and  auditory  tube.  It  also  forms  a  part  of  the 
superficial  petrosal  nerve. 

In  the  neck  the  glossopharyngeal  nerve  gives  a  branch  to  the  m. 


THE    AUDITORY    NERVE  439 

stylopharyngeus  and  branches  that  pass  to  the  mucosa  of  the 
pharynx  directly  and  others  indirectly  (through  the  pharyngeal 
plexus).  Terminal  brandies  pass  to  the  tonsil  and  mucosa  of  the 
dorsal  one-third  of  the  tongue. 

Auditory  Nerve  (Nervus  Acusticus). — This  nerve  comprises  really 
two  distinct  nerves  called  cochlear  and  vestibular  divisions  of  the 
auditory  nerve;  these  are  both  connected  with  special  sense,  the 
former  hearing,  and  the  latter,  the  sense  of  equilibrium,  if  this  term 
might  be  used.  As  in  the  case  with  all  of  the  real  cerebral  sensor 
nerves  there  is  a  ganglion  connected  with  each  division  comparable 
to  the  ganglion  on  the  sensor  divisions  of  the  spinal  nerves.  The 
fibers  of  the  cochlear  division,  the  real  nerve  of  hearing,  arise  from 
the  bipolar  cells  of  the  ganglion  spiralc  located  in  the  internal  ear. 
These  myelinated  axones  pass  into  the  ventral  surface  of  the  brain 
stem,  in  connection  with  the  vestibular  division,  at  the  lower  (caudal) 
border  of  the  pons  at  its  junction  with  the  brachium  pontis.  After  a 
short  course  the  fibers  terminate  in  the  ventral  and  dorsal  cochlear 
nuclei.  These  nuclei  lie  upon  the  lateral  and  ventral  aspect  of  the 
restiform  body,  respectively. 

The  fibers  arising  from  the  cells  of  the  ventral  cochlear  nucleus 
pass  transversely  through  the  ventral  part  of  the  tegmentum,  just 
dorsal  to  the  pons  fibers,  and  form  here  the  trapezium;  here  fibers  are 
added  from  the  superior  olive  of  both  sides  and  from  the  cells  of  the 
trapezial  nuclei.  All  of  these  fibers  cross  the  midline  and  form  the 
lateral  lemniscus  that  ends  in  the  inferior  quadrigeminal  and  medial 
geniculate  bodies.  From  these  structures  new  fibers  continue  to 
the  auditory  center  in  the  cortex  of  the  temporal  lobe. 

In  the  lateral  lemniscus  are  cells  constituting  the  nucleus  of  the 
lateral  lemniscus  (a  way-station  in  the  auditory  pathway).  Here 
some  of  the  lemniscal  fibers  may  end  and  then  new  ones  replace 
them. 

The  fibers  from  the  dorsal,  or  lateral  cochlear  nucleus  have  a  dif- 
ferent course.  They  pass  over  the  restiform  body  to  the  floor  of 
the  fourth  ventricle,  where  most  of  them  continue  superficially  as 
the  strim  acusticce,  to  the  median  sulcus,  cross  the  midline,  pass 
ventrally  in  an  oblique  manner  and  join  the  lateral  lemniscus  of  the 
opposite  side.  Some  of  the  fibers  pass  to  the  lemniscal  nucleus  of 
the  same  side  from  which  new  fibers  join  the  trapezium  and  pass  to 
the  lemniscus  of  the  opposite  side.  All  of  the  fibers  terminate  as 
those  of  the  ventral  nucleus  do. 

The  fibers  of  the  vestibular  division  arise  from  the  bipolar  cells  of 
the  ganglion  vestibnlare  that  lies  in  the  internal  auditory  meatus. 
They  enter  the  brain  stem  with  the  cochlear  division.  Some  of  the 
fibers  ascending  end  in  the  medial  vestibular  nucleus;  others  descend- 
ing end  in  the  spinal  vestibular  nucleus;  still  others  terminate  within 


440 


THE    NERVE    SYSTEM 


the  lateral  vestibular  nucleus  [Deiter's)  and  the  remainder  pass  to  the 
superior  nucleus  of  Beckterew.  From  these  nuclei  fibers  pass  in 
various  directions  to  the  dentate  nucleus  and  nucleus  fastigii  of  the 


IN f  ROOT  ^ 

ft£OL     LEM. 


Fin.  316. — Diagram  of  the  nuclei  of  termination  of  the  vestibula 
connections. 


nd  their  higher 


Pic.  317. — Diagram  of  the 


nuclei  of  termination   and   their  higher  connections. 


cerebellum,  to  the  nuclei  of  the  oculomotor,  trochlear,  trigeminus  and 
abducens  nerve,  to  the  temporal  lobe  of  the  cerebral  cortex,  to  the 
thalamus  and  to  the  ventral  horns  of  the  spinal  cord  (cervical 
portion). 


THE    FACIAL    NERVE  441 

The  lateral  lemniscus  contains  all  of  the  auditory  fibers  but  they 
reach  this  tract  by  different  routes  as  shown  above. 

The  auditory  nerve  is  attached  to  the  brain  at  the  inferolateral 
margin  of  the  pons  lateral  to  the  facial  nerve.  It  consists  of  ves- 
tibular and  cochlear  roots.  It  passes  into  the  internal  acoustic  meatus. 
The  vestibular  root,  or  nerve  communicates  with  the  nervus  inter- 
medius  and  the  geniculate  ganglion  of  the  facial  nerve  and  sends  its 
three  branches  to  the  utriculus  and  ampulla?  of  the  superior  and 
lateral  semicircular  canals.  The  cochlear  root,  or  nerve  sends 
branches  to  ampulla  of  the  posterior  semicircular  canal,  to  the 
sacculus  and  the  cochlea.  The  vestibular  nerve  has  the  vestibular 
ganglion  and  the  cochlear  nerve  the  spiral,  or  cochlear  ganglion. 

The  Facial  Nerve  (Nervus  Facialis). — The  facial  nerve  consists  of 
two  distinct  nerves,  the  facial  proper  (motor)  and  the  nervus  intermedins 
(sensor). 

The  nucleus  of  origin  of  the  motor  portion  is  deeply  placed  and 
lies  in  the  ventral  part  of  the  tegmental  part  of  the  pons  well  to  the 
side  of  the  midline.  It  is  just  above  (cephalad  of)  the  boundary 
between  the  oblongata  and  pons.  The  axones  of  these  cells  have 
a  decidedly  peculiar  course.  They  pass  first  dorsally  almost  to 
the  ventricular  surface,  then  arch  over  the  nucleus  of  the  abducens 
nerve  (toward  the  midline),  then  pass  ventrally  and  emerge  from  the 
brain  stem  at  the  lower  border  of  the  pons  at  the  medial  side  of  the 
auditory  nerve. 

The  fibers  of  the  nervus  intermedius  are  both  motor  and  sensor 
fibers;  the  sensor  portion  arises  from  the  unipolar  cells  of  the  gen- 
iculate ganglion  in  the  facial  canal.  The  dendrites,  that  pass  per- 
ipherally, constitute  the  chorda  tympani  nerve  (taste)  and  the  central 
fibers  (axones)  constitute  the  intermediate  nerve.  They  enter  the 
brain  stem  between  the  facial  and  auditory  nerves  and  terminate  in 
the  upper  end  of  the  nucleus  of  the  fasciculus  solitarius  (glossopharyn- 
geus).  The  motor  fibers  are  said  to  arise  from  the  cells  in  a  nucleus 
near  the  midline  and  beneath  the  ventricular  gray  substance  (nucleus 
salivatorius) .  This  is  said  to  extend  from  the  level  of  the  facial 
nerve  to  the  level  of  the  lower  end  of  the  motor  nucleus  of  the 
trigeminal  nerve.     These  represent  excito  glandular  fibers. 

The  facial  nerve  arises  from  the  brain  at  the  inferolateral  margin 
of  the  pons  just  medial  to  the  auditory  nerve.  It  passes  into  the 
internal  acoustic  meatus  with  the  acoustic  nerve,  then  through  the 
facial  canal  of  the  petrous  portion  of  the  temporal  bone  and  appears 
upon  the  base  of  the  skull  through  the  stylomastoid  foramen.  It 
then  passes  through  the  parotid  gland  (branching  here)  to  supply  the 
muscles  of  the  face.  The  geniculate  ganglion  is  situated  upon  the 
facial  nerve  in  the  facial  canal  and  gives  off  the  greater  superficial 
petrosal,  deep  petrosal  and  externa!  superficial  petrosal  nerves;  the 
deep  nerve  passes  to  the  sphenopalatine  ganglion. 


44 -1 


THE    XERVE    SYSTEM 


In  the  facial  canal  the  nerve  gives  off  a  branch  to  the  m.  stapedius 
and  the  chorda  tympani  nerve.  The  latter  passes  through  the 
tympanic  cavity  and  petrotympanic  fissure  to  join  the  lingual 
branch  of  the  mandibular  nerve. 

In  the  neck  the  facial  nerve  gives  branches  to  the  mm.  stylohyoideus 
and  digastricus  (posterior  belly),  auricularis  posterior  and  occipitalis 
and  the  intrinsic  muscles  of  the  auricle. 

In  the  parotid  gland  the  facial  nerve  forms  the  parotid  plexus  con- 
stituting cervicofacial  and  temporofacial  divisions.     The  cervicofacial 

Nucleus  Salivatori  us 
,  Motor  part  of  M  Intermedins  _ 
Meryus  Intermedius 

Geniculate  Garty/>o"  Maxi  llary  Mei 


Posterior /luricularh. 


To  Dioastnc^ 
To  Stylohyoid. 


Fig.  318. — Diagram  of  the  facial  and  intermediate  nerves  and  their  connections. 

division  gives  off  the  following  branches:  Buccal  branches  to  the 
m.  buccinator  and  muscles  at  the  angle  of  the  mouth;  the  marginal, 
or  supramandibidar.  branch  of  the  mandible  that  supplies  the  mm. 
orbicularis  oris  and  the  quadratus  labii  inferioris.  The  cervical,  or 
iniramandibular,  branch  supplies  the  m.  platysma. 

The  temporofacial  division  gives  off  the  temporal  branches  that 
supply  the  mm.  orbicularis  oculi,  corrugator  supercilii,  frontalis  and 
auricularis  anterior  and  posterior.  The  zygomatic  branches  supply 
the  mm.  orbicularis  oculi  and  zygomaticus. 

The  Abducens  Nerve  (Nervus  Abdmois). — This  is  a  small  motor 
nerve  the  fibers  of  which  arise  from  the  cells  of  the  nucleus  located 
under  the  dorsal  part  of  the  tegmental  portion  of  the  pons  near  the 
midline.     The  axones  pass  ventrally  and  laterally  and  emerge  from 


THE    TRIGEMINAL    NERVE  443 

the  brain  stem  along  the  lower  border  of  the  pons  near  the  midline 
(superficial  origin). 

The  abducent  nerve  passes  through  the  middle  fossa  along  the 
carotid  artery  and  enters  the  orbital  fossa  through  the  superior 
orbital  fissure  to  supply  the  m.  rectus  lateralis. 

The  Trigeminal  Nerve  {Nerous  Trigeminus). — This  represents  a 
mixed  nerve  and  is  the  largest  of  the  cerebral  nerves.  Its  nuclei 
of  origin  and  termination  are  the  most  widely  distributed  and  longest 
of  all  the  nerves,  extending  from  the  midbrain  through  the  pars 
dorsalis  pontis  and  the  oblongata  into  the  spinal  cord. 

The  nucleus  of  origin  of  the  motor  portion  consists  of  two  parts,  a 
principal  nucleus  that  lies  close  to  the  sensor  nucleus,  though  dorsal 
thereto,  near  the  lateral  aspect  of  the  pars  dorsalis  pontis.  The 
mesencephalic  nucleus  starts  just  a  little  above  (cephalad  of)  the 
preceding  and  extends  throughout  the  midbrain  and  is  seen  at  the 
extreme  lateral  limit  of  the  gray  substance  of  the  aqueduct.  Where 
it  starts  it  is  quite  large  but  the  midbrain  portion  gradually  tapers. 
The  fibers  arising  from  these  two  nuclei  pass  ventrally  and  emerge 
from  the  brain  stem  at  the  junction  of  the  pons  and  brachium  pontis 
of  each  side  serving,  thus,  as  an  arbitrary  boundary  between  these 
two  structures.  The  greater  part  of  the  motor  root  consists  of  the 
axones  of  the  principal  nucleus.  The  two  nuclei  are  connected  to 
each  other  by  collateral  fibers.  These  nuclei  receive  fibers  from  the 
motor  area  of  the  cerebral  cortex  through  the  opposite  pyramid. 

The  sensor  portion  consists  of  the  axones  of  the  cells  in  the  semi- 
lunar ganglion  (ganglion  scmilunare)  located  upon  the  apex  of  the 
petrous  portion  of  the  temporal  bone.  It  is  larger  than  the  motor 
root  and  enters  the  brain  stem  where  the  motor  root  emerges.  In 
the  brain  stem  the  fibers  bifurcate,  one  branch  ascending  and  ending 
in  the  main  sensor  nucleus  that  lies  near  the  surface  of  the  tegmental 
part  of  the  pons,  ventral  to  the  brachium  conjunctivum.  This 
nucleus,  like  the  corresponding  motor  nucleus,  extends  into  the 
midbrain,  tapering  as  it  ascends.  The  descending  branches  form  a 
large  tract  called  the  descending  root  of  the  trigeminal  nerve.  The 
tract  lies  just  lateral  to  the  substantia  gelatinosa;  at  intervals  the 
fibers  end  around  the  cells  of  the  substantia  gelatinosa  and  they 
represent  the  nucleus  of  termination  of  the  descending  root.  This 
descending  root  decreases  in  size  as  it  approaches  the  spinal  cord  and 
ends  at  the  level  of  the  first  or  second  cervical  nerve.  From  these 
terminal  nuclei  fibers  (arcuata)  pass  through  the  raphe  to  the  oppo- 
site side  and  proceed  upward  to  the  thalamus  where  new  fibers  arise 
and  pass  to  the  sensor  area  of  the  cerebral  cortex.  Some  fibers  pass 
from  the  sensor  to  the  motor  nucleus  thus  establishing  a  simple 
reflex  arc. 

The  trigeminal  nerve  is  attached  to  the  brain  at  the  middle  of  the 


444 


THE    NERVE    SYSTEM 


lateral  border  of  the  pons.  It  consists  of  two  roots,  the  larger,  sensor 
and  the  smaller,  motor.  As  these  two  roots  pass  forward  and  reach 
the  apex  of  the  petrous  portion  of  the  temporal  hone  the  sensor  root 
exhibits  an  enlargement,  the  semilunar,  or  Gasserian  ganglion. 
From  this  ganglion  Hirer  roots,  or  nerves,  are  seen  to  arise,  the  ophthal- 
mic, maxillary  and  mandibular  nerves.  The  motor  root  is  hidden  by 
the  ganglion  and  it  joins  the  mandibular  nerve. 

The  ophthalmic  nerve  passes  through  the  middle  fossa  to  enter 
the  orbital  fossa  through  the  superior  orbital  fissure      It  gives  rise 

Trigeminal   Gasserian    Ophthalmic  nerve 
or  5th  nerve    ganglion 


Sphenopa 


Inf.  alveolar  nerve 

Fig.  319. — The  trigeminal  nerve  and  its  communications  with  the  facial  and  glosso- 
pharyngeal nerves.  {After  Sobotta  and  Mc&turrich.)  The  exposed  nerves  are  black,  the 
concealed  ones  shaded. 


lo  three, main  branches.  The  lacrimal  nerve  gives  branches  to  the 
lacrimal  gland,  the  conjunctiva  and  skin  at  the  lateral  commissure  of 
the  eyelids.  The  frontal  nerve,  through  its  supratrochlear  branch, 
supplies  the  skin  of  the  root  of  the  nose,  the  medial  commissure  of  the 
eyelids  and  the  medial  part  of  the  forehead.  Through  its  larger 
supraorbital  branch  it  supplies  the  frontal  sinus,  the  skin  of  the 
upper  eyelid  and  of  the  forehead  and  scalp  to  the  vertex.  The 
nasoi  iliary  nerve,  in  the  orbit,  gives  a  branch  to  the  ciliary  ganglion, 
gives  off  the  infratrochlear  nerve,  that  supplies  the  skin  of  the  root  of 
the  nose  and  the  eyelids.  In  the  nose  it  gives  off  the  lateral  and 
medial  nasal  branches  that  supply  the  mucosa  of  the  lateral  wall  and 
septum  of  the  nose.  On  the  face  the  external  nasal  branch  supplies 
the  skin  of  the  lower  half  of  the  tip  of  the  nose. 

The  ciliary  ganglion,  connected  with  this  division  of  the  trigeminal 
nerve,  is  a  small  reddish  ganglion  in  the  orbit.     It  has  three  roots; 


THE    TRIGEMINAL    NERVE  445 

the  long,  or  sensory  root,  is  derived  from  the  nasociliary  nerve;  the 
short,  or  motor  root  is  derived  from  the  oculomotor  nerve;  the  sym- 
pathetic root  is  derived  from  the  cavernous  plexus  of  the  sympathetic 
system  upon  the  internal  carotid  artery.  This  ganglion  gives  rise 
to  about  fifteen  short  ciliary  nerves  that  supply  the  coats  of  the  eyeball 
and  the  muscles  of  the  ciliary  body  and  iris. 

The  maxillary  nerve,  the  largest  division,  leaves  the  middle  fossa 
of  the  skull  through  the  foramen  rotundum,  passes  through  the 
pterygopalatine  fossa  where  it  gives  off  a  number  of  branches.  The 
remainder  of  the  nerve  enters  the  orbit  as  the  infraorbital  nerve, 
passes  through  the  infraorbital  canal  (giving  off  branches)  and 
appears  upon  the  face  through  the  infraorbital  foramen. 

In  the  pterygopalatine  fossa  it  gives  off  the  following  branches: 
Two  branches  to  the  sphenopalatine  ganglion;  posterior  superior 
alveolar  nerves,  for  the  molar  teeth  and  the  neighboring  parts  of  the 
gum.  The  zygomatic,  or  orbital  branch,  that  divides  into  zygomatico- 
temporal or  temporal  nerve  (for  the  skin  of  the  temple)  and  the 
zygomaticofai  ial,  or  malar  nerve  (for  the  skin  over  the  zygomatic  bone) . 

In  the  infraorbital  canal  the  infraorbital  nerve  gives  off  the  middle 
and  anterior  superior  alveolar  nerves  that  supply  the  premolar,  canine 
and  incisor  teeth,  the  gum  and  the  mucosa  of  the  maxillary  sinus. 

Upon  the  face  the  infraorbital  nerve  gives  off  the  inferior  palpebral 
branches,  for  the  lower  eyelid;  the  external  nasal,  for  the  skin  of  the 
side  of  the  nose;  the  superior  labial,  for  cheek  and  upper  lip. 

The  sphenopalatine  ganglion  is  connected  with  this  division  of  the 
trigeminal  nerve,  in  the  pterygopalatine  fossa,  by  the  two  spheno- 
palatine (sensor)  roots.  The  motor  root  comes  from  the  geniculate 
ganglion  of  the  facial  nerve  (through  the  greater  superficial  petrosal 
nerve)  and  the  sympathetic  root  comes  from  the  cavernous  plexus 
(through  the  deep  petrosal  nerve).  These  last  two  named  nerves 
form  the  nerve  of  the  pterygoid  canal.  This  ganglion  gives  off  the 
following  branches:  Pharyngeal  branches,  to  the  mucosa  of  the  roof 
of  the  pharynx.  The  anterior  palatine  nerves,  for  the  mucous  mem- 
brane of  the  mucosa  of  the  soft  and  hard  palate  and  a  part  of  the 
lateral  wall  of  the  nasal  fossa.  The  middle  palatine  nerve,  for  the 
mucosa  of  the  uvula,  soft  palate  and  palatal  tonsil.  The  posterior 
palatine  nerve  supplies  the  mucosa  of  the  same  region.  The  posterior 
superior  nasal  nerve,  for  that  portion  of  the  lateral  wall  of  the  nasal 
fossa.  The  nasopalatine  nerve,  for  the  mucous  membrane  of  the 
roof  and  nasal  septum  and  the  hard  palate.  Orbital  branches,  to  the 
periosteum  of  the  orbit. 

The  mandibular  nerve  contains  all  of  the  motor  fibers  and  some 
sensor  fibers.  These  two  parts  are  separate  and  leave  the  middle 
fossa  of  the  skull  through  the  foramen  ovale,  enter  the  infratemporal 
fossa,  fuse  and  divide  into  anterior  and  posterior  divisions. 


446  THE    NERVE    SYSTEM 

The  branches  of  the  undivided  nerve  are  the  spinous,  or  recurrent 
nerve,  that  supplies  the  dura  and  a  branch  to  the  m.  pterygoideus 
internus. 

The  masticator  nerve,  or  anterior  branch,  gives  off  a  branch  to  the 
m.  pterygoideus  externus;  one,  to  the  m.  masseter;  two,  to  the  m. 
temporalis;  a  buccinator  branch  (sensor)  that  supplies  the  skin  and 
mucosa  of  the  cheek. 

The  Larger  posterior  branch  gives  off  the  following  branches:  The 
auriculotemporal  nerve  (by  two  roots)  that  supplies  the  skin  and 
scalp  of  the  temporal  region,  the  mandibular  articulation,  the  paro- 
tid gland,  the  skin  of  the  external  auditory  canal  and  the  tympanic 
membrane. 

The  Lingual  nerve  is  one  of  the  terminal  branches  of  the  mandibular 
nerve.  It  supplies  the  mucosa  of  the  apical  two-thirds  of  the  tongue, 
the  floor  and  lateral  walls  of  the  mouth  and  sends  a  branch  to  the 
submaxillary  ganglion.  It  is  joined  by  the  chorda  tympani  and 
branches  from  the  hypoglossal  nerve. 

The  inferior  alveolar,  or  dental  nerve,  is  the  larger  terminal  branch 
of  the  mandibular  nerve.  This  gives  off  the  mylohyoid  nerve,  for 
the  muscle  of  the  same  name  and  the  anterior  belly  of  the  digastricus. 
It  then  enters  the  mandibular  canal,  through  the  mandibular 
foramen.  Here  it  gives  off  branches  to  the  molar  and  premolar  teeth 
and  the  mental  nerve  and  then  terminates  in  branches  for  the  canine 
and  incisor  teeth.  The  mental  nerve  leaves  the  mandibular  canal 
through  the  mental  foramen  and  supplies  the  chin  and  lower  lip. 

The  submaxillary  ganglion  is  connected  with  the  lingual  nerve. 
Its  motor  root  is  derived  from  the  chorda  tympani;  its  sensor  root  is 
derived  from  the  lingual  nerve;  its  sympathetic  root  is  derived  from 
the  sympathetic  plexus  of  the  external  maxillary  artery.  Its 
branches  are  distributed  to  the  submaxillary  gland  and  duct. 

The  otic  ganglion  is  situated  near  the  mandibular  nerve  as  it 
emerges  from  the  foramen  ovale.  Its  motor  root  is  derived  from  the 
nerve  to  the  m.  pterygoideus  internus;  its  sensor  root  is  derived  from 
the  tympanic  plexus  (through  the  smaller  superficial  petrosal  nerve); 
the  sympathetic  root  is  derived  from  the  sympathetic  plexus  upon  the 
middle  meningeal  artery.  It  sends  branches  to  the  nerve  of  the 
pterygoid  canal,  the  chorda  tympani  and  roots  of  the  auriculotem- 
poral nerves;  its  two  motor  branches  supply  the  mm.  tensor  veli  pala- 
tini and  tensor  tympani. 

The  Trochlear  Nerve  (Nerous  Trochlearis). — This  is  a  pure  motor 
nerve  that  has  its  nucleus  of  origin  in  the  midbrain.  This  nucleus 
is  small  and  oval  and  lies  in  the  gray  substance  of  the  floor  of  the 
aqueduct  beneath  the  inferior  quadrigeminal  body  of  each  side.  It 
rests  upon  the  median  longitudinal  fasciculus  and  lies  close  to  the 
midline.     The  axones  arising  from  these  cells  pass  downward  (cau- 


THE    OCVLOMOTOR    XERVE 


447 


dally)  and  laterally  along  the  edge  of  the  aqueduct  gray  which  they 
follow  to  the  midline;  here  the  nerves  decussate  at  the  upper  edge 
of  the  superior  medullar}-  velum  and  emerge  at  the  medial  border 
of  the  brachia  conjunctiva.  They  are  the  smallest  of  the  cerebral 
nerves.  These  nuclei  receive  fibers  from  the  motor  area  of  the 
opposite  cerebral  cortex  through  the  pyramid.  Fibers  of  the  median 
longitudinal  fasciculus  also  end  here. 

The  trochlear  nerve  arises  from  the  midbrain  just  behind  the  cor- 
pora quadrigemina.  It  passes  to  the  ventral  surface  of  the  brain 
stem  and  through  the  middle  fossa  of  the  skull  to  enter  the  orbital 
fossa  through  the  superior  orbital  fissure.  It  supplies  the  m.  ob- 
liquus  superior. 

The  Oculomotor  Nerve  (Nervus  Ocidomotorius). — This  is  also  a 
pure  motor  nerve  and  its  nucleus  of  origin  is  also  in  the  midbrain. 


Fig.  320. — Xuclei  of  origin  of  the  motor  cerebral  nerves  (lateral  view) 


The  nucleus  is  quite  large,  5  to  6  mm.  long  and  lies  in  the  floor  of 
the  aqueduct  gray  substance  under  the  superior  quadrigeminal 
bodies  just  ahead  of  the  preceding  nucleus;  it  rests  upon  the  median 
longitudinal  fasciculus.  The  cells  do  not  form  a  single  mass  but 
are  arranged  into  a  number  of  fairly  distinct  groups  (at  least  seven) 
in  each  nucleus  and  a  common  small  nucleus  in  the  midline,  the 
central  nucleus.  Most  of  the  fibers  of  each  nerve  arise  from  the 
nucleus  of  the  same  side  and  pass  ventrally  in  bundles;  when  the  red 
nucleus  is  reached  they  spread  out  and  pass  through  it,  to  be  gathered 
into  compact  bundles  at  its  ventral  limit.  These  bundles  are  then 
collected  into  a  single  mass  that  emerges  upon  the  medial  aspect  of 
each  cerebral  peduncle  (intercrural  space)  in  the  oculomotor  sulcus 
(the  groove  between  the  crusta  and  tegmentum  of  the  crus). 


448  THE    NERVE    SYSTEM 

The  fibers  from  the  central  nucleus,  and  possibly  other  nuclei,  de- 
cussate immediately  and  join  the  opposite  nerve.  These  fibers  are 
probably  those  that  innervate  the  medial  rectus  muscle. 

The  oculomotor  nucleus  is  connected  to  the  occipital  cortex 
(visual  area)  through  the  optic  radiation;  with  other  cerebral  nerves 
through  the  median  longitudinal  fasciculus;  with  the  motor  area  of 
the  cerebral  cortex  through  the  pyramid;  with  the  visual  apparatus 
through  fibers  from  the  superior  quadrigeminal  body. 

The  oculomotor  nerve  emerges  from  the  ventral  surface  of  the  mid- 
brain in  the  oculomotor  sulcus  and  passes  forward  to  enter  the  orbital 
fossa  through  the  superior  orbital  fissure.  It  supplies  the  mm.  recti 
superior,  inferior,  medialis,  the  levator  palpebrae  and  obliquus  in- 
ferior; it  also  sends  a  branch  to  the  ciliary  ganglion. 

The  Optic  Nerve  (X  err  us  Opticus). — As  previously  mentioned  this 
is  not  considered  as  a  true  cerebral  nerve  and  is  best  considered  as 
the  optic  tract.  This  tract  comprises  the  optic  nerves  and  the  optic 
chiasm  as  the  peripheral  parts  and  the  pulvinar  (of  thalamus)  the 
lateral  geniculate  body,  the  superior  quadrigeminal  body  and  the 
occipital  cortex  as  the  central  parts. 

The  optic  nerve  arises  in  the  retina  of  the  eyeball.  The  fibers 
proceed  in  a  peculiar  manner.  Upon  reaching  the  ventral  part  of 
the  brain  in  the  region  of  the  thalamus,  the  fibers  from  the  nasal  side 
of  each  retina  (about  two-thirds)  cross  the  midline,  decussate,  form- 
ing the  optic  chiasm  and  those  parts  usually  called  the  optic  tracts. 
In  addition  the  caudal  side  of  the  chiasm  contains  added  fibers  the 
commissure  of  Gudden,  a  group  of  fibers  that  connect  one  medial 
geniculate  body  with  the  other;  so  far  as  is  known  these  fibers  have 
no  part  in  the  visual  pathway  but  form  the  so-called  medial  root  of 
the  optic  tract. 

The  optic  tract  after  leaving  the  chiasm  bends  dorsally  around  the 
crus  cerebri  of  each  side  and  divides  into  a  medial  and  a  lateral  root. 
The  medial  root  ends  in  the  medial  geniculate  body  and  represents,  the 
commissure  of  Gudden  above  mentioned.  The  lateral  root  is  the  real 
continuation  of  the  visual  portion  of  the  chiasm  and  ends  in  the  lower, 
or  primary  optic  centers,  i.e.,  the  lateral  geniculate  body,  the  pulvinar 
and  the  superior  quadrigeminal  body  of  that  side.  The  first  named 
receives  the  most  of  the  fibers  and  the  last  the  least,  as  it  is  concerned 
only  with  muscle  reflexes  and  not  with  light,  or  color  perception. 
From  its  cells  fibers  join  the  optic  nerve  and  end  in  the  retina. 

The  lateral  geniculate  body  and  pulvinar  of  the  thalamus  are  im- 
portant subcenters  for  vision.  From  these  centers  new  fibers  arise 
and  pass  in  a  compact  bundle  toward  the  occipital  cortex  (cuueus) 
where  they  end  around  the  occipital  cells.  In  addition,  fibers  pass 
from  these  occipital  cells  and  end  in  the  superior  quadrigeminal  body 
and  pulvinar  of  the  same  side.  All  of  these  fibers  and  the  caudal 
part  of  the  internal  capsule  constitute  the  optic  radiation. 


THE    SPINAL    NERVES  449 

The  superior  quad ri gem inal  body  is  connected  with  the  nuclei 
of  the  motor  nerves  of  the  eyeball  by  means  of  fibers  that  arise  from 
its  cells  and  enter  the  median  longitudinal  fasciculus.  This  body  is 
also  connected  with  the  oblongata  and  the  spinal  cord  through  the 
medial  lemniscus. 

From  the  optic  chiasm  the  optic  nerve  may  be  followed  through 
the  optic  foramen  to  the  dorsal  portion  of  the  eyeball.  Its  connec- 
tion with  the  eyeball  is  described  under  that  organ. 

Olfactory  Nerve  (Nervus  Olfactorius). — This  is  not  a  single  nerve 
upon  each  side  but  about  twenty  nerves,  or  fila;  these  arise  from  the 
cells  of  the  nasal  mucosa,  pass  through  the  cribriform  plate  of  the 
ethmoid  bone  and  terminate  in  the  olfactory  bulb.  The  details 
of  the  remainder  of  the  tract  have  been  considered  under  the 
"Olfactory  Pathway." 

THE  SPINAL  NERVES 

The  spinal  nerves  are  arranged  in  pairs  of  which  there  are  usually 
thirtv-one.  Each  nerve  consists  of  two  portions,  or  roots  called 
ventral,  or  motor  and  sensor,  or  dorsal.  These  nerves  pass  from  the 
vertebral  canal  through  the  intervertebral  foramina.  Within  the 
vertebral  canal  the  roots  are  distinct  and  separate,  but  peripheral  to 
the  foramina  the  roots  are  united  together  into  a  single  mass,  the 
nerve  proper.  These  nerves  are  named  according  to  the  vertebra 
between  which  they  pass.  Each  nerve  passes  beneath  its  correspond- 
ing vertebra  except  the  first  cervical  pair  that  emerges  between  the 
occipital  bone  and  the  atlas  and  should  really  be  called  the  suboc- 
cipital nerve.  Occasionally  the  thirty-first  pair  is  absent,  or  two 
additional  pairs  may  be  present.  These  latter  are  small  and  do  not 
emerge  from  the  vertebral  canal;  they  represent  rudimentary  caudal 
nerves. 

The  nerves  are  as  follows: 

Cervical . .      8  pairs. 

Thoracic.  . .  12  pairs. 

Lumbar 5  pairs. 

Sacral ....      5  pairs. 

Coccygeal .    .  i  pair. 

Each  spinal  nerve  consists  of  a  ventral  and  a  dorsal  root.  The 
ventral,  or  motor  root  consists  of  myelinated  axones  of  the  cells  in 
the  ventral  horns  of  the  spinal  gray  substance.  The  roots  emerge 
from  the  ventrolateral  region  in  a  linear  formation,  indicating  a 
segmentation  of  the  cord.  The  ventral  roots  are  smaller  than  the 
dorsal  but  the  individual  fibers  are  larger.  These  fibers  are  both 
somatomotor  and  visceromotor. 

Within  each  intervertebral  foramen  lies  a  ganglion  connected  with 
each  dorsal  root.     The  central  end  of  the  root  (that  which  enters 


450  THE    NERVE    SYSTEM 

the  cord)  is  made  up  of  the  myelinated  axones  of  the  ganglion  cells 
in  these  ganglia;  the  peripheral  part  of  the  root  (that  which  joins  the 
motor  root  to  form  the  nerve  proper)  consists  of  the  myelinated 
dendrites  of  the  cells  in  the  ganglia. 

Each  spinal  nerve,  after  the  junction  of  its  two  roots,  is  a  mixed 
nerve;  a  short  distance  from  this  junction  each  nerve  divides  into  a 
dorsal  and  a  ventral  primary  division,  or  ramus,  each  of  which  con- 
sists of  motor  and  sensor  fibers.  Each  dorsal  ramus  divides  into  a 
medial  and  a  lateral  trunk.  The  medial  branches,  in  the  upper  half 
of  the  body  contain  the  cutaneous  nerves  while  the  lateral  branches 
contain  the  muscular  nerves;  in  the  lower  half  of  the  body  the  reverse 
condition  prevails.  Certain  spinal  nerves  send  branches  to  the  sym- 
pathetic system  and  these  constitute  the  white  rami  communicantes. 

Those  spinal  nerves  that  are  intended  for  the  appendages  are  the 
largest,  as  the  lower  cervical  and  first  thoracic  for  the  pectoral 
appendage  and  the  lower  lumbar  and  upper  sacral  for  the  pelvic 
appendage.  These  nerves  form  the  great  brachial  and  lumbar  plexuses 
upon  each  side,  for  the  pectoral  and  pelvic  appendages,  respectively. 

THE  DORSAL  RAMI  OF  THE  SPINAL  NERVES 
THE  CERVICAL  NERVES 

The  first  cervical,  or  suboccipital  nerve  has  a  rudimentary  dorsal 
root  usually.  Its  dorsal  ramus  is  large.  The  nerve  passes  into  the 
neck  and  gives  off  muscular  branches  to  the  mm.  semispinalis  capitis, 
recti  capitis  posterior  major  and  minor  and  the  obliqui  capitis 
superior  and  inferior.  It  sends  a  communicating  branch  to  the  second 
cervical  nerve. 

The  dorsal  ramus  of  the  second  cervical  nerve  is  larger  than  its 
ventral  ramus  and  passes  into  the  neck.  It  distributes  muscular 
branches  to  the  mm.  semispinales  capitis  and  cervicis,  the  obliquus 
inferior  and  the  multifidus.  It  sends  communicating  branches  to  help 
form  the  dorsal  cervical  plexus.  A  large  part  of  this  ramus  accom- 
panies the  occipital  artery  as  the  great  occipital  nerve  which  is  the 
chief  cutaneous  nerve  of  the  back  of  the  scalp. 

The  third  cervical  nerve  is  small  and  its  dorsal  ramus  divides  into 
medial  branch  that  becomes  the  third  occipital  nerve  and  supplies  the 
skin  of  the  scalp  and  neck.  The  lateral,  or  muscular  branch,  supplies 
contiguous  muscles. 

The  dorsal  rami  of  the  rest  of  the  cervical  nerves  are  quite  small. 
Their  medial  branches  are  cutaneous  for  the  skin  of  the  back  of  the 
neck  and  their  lateral  branches  supply  the  surrounding  muscles. 

THE  THORACIC  REGION 

Each  dorsal  ramus  divides  into  medial  and  lateral  branches.  The 
medial  branches  of  the  first  seven  thoracic  nerves  are  chiefly  cuta- 
neous for  the  scapular  region.     The  lateral  branches  supply  branches 


THE    SPINAL    NERVES  45I 

to  the  longitudinal  muscles  of  the  back.  In  the  lower  thoracic 
region  the  lateral  branches  are  cutaneous,  supplying  the  skin  of  the 
back  as  low  as  the  buttock.  The  medial  branches,  here,  supply 
branches  to  the  longitudinal  muscles  of  the  back. 

THE  LUMBAR  REGION 

The  dorsal  rami  of  the  first,  second  and  third  lumbar  nerves  divide 
into  medial  and  lateral  branches.  The  medial  branches  innervate 
the  deep  muscles  of  the  back  while  the  lateral  branches  are  chiefly 
cutaneous  and  supply  the  skin  of  the  buttock. 

The  dorsal  rami  of  the  fourth  and  fifth  lumbar  nerves  are  chiefly 
muscular  and  send  branches  to  the  longitudinal  muscles  of  the  back. 

THE  SACRAL   AND  COCCYGEAL  REGIONS 

The  dorsal  rami  of  the  first,  second  and  third  sacral  nerves  supply  the 
m.  multifidus  through  their  medial  muscular  branches,  and  the  skin  of 
the  sacral  and  adjoining  buttock  region,  through  their  lateral 
cutaneous  branches. 

The  dorsal  rami  of  the  fourth  and  fifth  sacral  nerves  and  that  of  the 
coccygeal  nerve  form  the  posterior  anococcygeal  nerve,  which  is  a 
cutaneous  nerve  for  the  skin  of  the  coccyx  region. 

THE  VENTRAL  RAMI  OF  THE  SPINAL  NERVES 

The  ventral  rami  of  the  spinal  nerves  are,  with  the  exception  of  those 
of  the  thoracic  region,  concerned  in  the  formation  of  extensive  plex- 
uses. Each  usually  receives  a  gray  ramus  communicans  from  the 
sympathetic  system  and  many  give  off  a  delicate  white  ramus  com- 
munis ans  to  the  sympathetic  system. 

Each  thoracic  nerve  passes  ventrally  between  the  intercostal 
muscles,  supplying  branches  to  these  muscles.  At  the  side  of  the 
thorax  each  gives  off  a  lateral  branch  that  passes  to  the  subcutaneous 
tissues  and  branches  into  ventral  and  dorsal  divisions,  for  the  supply 
of  the  skin  of  the  side  of  the  thorax.  The  remainder  of  the  ventral 
ramus  continues  ventrally  between  the  intercostal  muscles  to  the 
margin  of  the  sternum  where  it  passes  to  the  subcutaneous  tissues 
to  be  distributed  to  the  skin  of  the  ventral  thoracic  region. 

THE  CERVICAL  PLEXUS  (PLEXUS   CERVICALIS1 

The  ventral  rami  of  the  first  four  cervical  nerves  form  the  cervical 
plexus,  under  cover  of  the  m.  sternomastoideus.  These  nerves  form 
irregular  loops  with  one  another  and  from  these  loops  superficial 
(cutaneous)  ascending  and  descending  and  deep  ( muscular  and  com- 
municating) branches  are  given  off. 

The  Superficial  Cutaneous  Branches. — Ascending  Branches. — The 
smaller  occipital  nerve  (C.  2,  3)  passes  toward  the  occiput  and  gives 


452 


THE    XERVE    SYSTEM 


off  the  mastoid,  auricular  and  occipital  branches  for  the  skin  of  the 
ear  and  mastoid  and  occipital  regions. 

The  great  auricular  nerve  (C.  2,  3)  passes  toward  the  ear  and  gives 
off  mastoid,  auricular  and  facial  branches  to  the  skin  of  those  regions; 
the  facial  branch  supplies  the  skin  of  the  cheek  and  over  the  masseter 
muscle  and  parotid  gland. 

The  cutaneous  cervical  nerve  (C.  2,  3)  supplies  the  skin  of  the 
anterior  triangle  of  the  neck. 

N.hypoyhssas 
to  m.rectus  capitis  latcraJi 


N  occipitalis  minor    it-*^-* 
Ramus  descendens  n.  hypoqlosii 
N auncularis  maynus 
N.  cutaneus  colii 


N.dorsolii,7°mU"at°r*C/VX'1' 
SCapulat\ja„Mrnomo, 


M  cutane, 
medial'! 
A/n.  mtercosfobrachiales 


(After  P.  Eisler.) 


Descending  Branches. — The  descending  roots  of  the  second  and 
third  cervical  nerves  unite  to  form  a  single  trunk  that  divides  into 
ventral,  middle  and  dorsal  branches.  The  ventral,  or  suprasternal 
branches  supply  the  skin  of  the  neck  and  upper  sternal  region.  The 
middle,  or  suprascapular  branches  supply  the  skin  of  the  over  the 
middle  third  of  the  clavicle  to  the  nipple.  The  dorsal,  or  supra- 
acromial,  branches  supply  the  skin  over  the  lateral  third  of  the  clavicle 
and  the  deltoid  region. 


THE    BRACHIAL    PLEXUS  453 

The  Deep  Branches. — These  are  lateral  and  medial.  The  muscular 
branches  of  the  lateral  division  are  to  the  mm.  sternomastoideus  (C.  2), 
trapezius  (C.  3,  4),  levator  scapulae  (C.  3,  4),  scaleni  medius  and 
posterior  (C.  3,  4).  The  communicating  branches  are  given  to  the 
accessory  nerve. 

The  medial  division  gives  muscular  branches  to  the  prevertebral 
muscles  as  follows:  mm.  rectus  capitis  lateralis,  longus  capitis,  rectus 
capitis  anterior  (C.  1,  2),  the  mm.  intertransversarium,  longus  colli 
and  longus  capitis  (C.  2,  3,  4),  the  m.  scalenius  anterior  (C.  4). 

The  descending  cervical  nerve  is  formed  by  small  branches  from 
the  second  and  third  cervical  nerves.  With  the  descendens  or  com- 
municans  hypoglossi  (derived  from  the  first  and  second  cervical 
nerves)  the  descending  cervical  nerve  forms  the  ansi  hypoglossi, 
which  sends  branches  to  the  mm.  sternohyoideus,  sternothyreoideus 
and  omohyoideus.  The  mm.  thyreoihyoideus  and  geniohyoideus 
are  also  supplied  by  the  first  and  second  cervical  nerves  by  a  branch 
that  accompanies  the  hypoglossal  nerve. 

The  phrenic  nerve  (11.  phrcnicus)  is  also  derived  from  the  descend- 
ing branches  of  the  third,  fourth  (mainly)  and  fifth  cervical  nerves. 
This  nerve  passes  down  through  the  neck  and  thorax  and  at  the 
diaphragm  supplies  this  organ  with  muscular  branches.  It  also 
gives  branches  to  the  pleura,  pericardium,  inferior  vena  cava,  supra- 
renal gland  and  liver.  The  last  two  are  not  direct,  however,  but 
through  the  diaphragmatic  sympathetic  plexus. 

The  communications  of  the  descending  cervical  branches  are  with 
the  superior  cervical  sympathetic  ganglia,  the  vagal  and  the  hypo- 
glossal nerves.  The  communications  of  the  phrenic  nerve  are  with 
the  cervical  sympathetics  and  the  celiac  and  diaphragmatic  plexuses. 

THE  BRACHIAL  PLEXUS  .PLEXUS  BRACHIALIS) 

The  brachial  plexus  is  the  extensive  plexus  from  which  are  derived 
the  nerves  for  the  superior  extremity.  It  is  formed  by  the  ventral 
rami  of  the  fifth,  sixth,  seventh  cervical  and  first  thoracic  nerves.  This 
plexus  lies  in  the  neck  and  axillary  space  and  gives  rise  to  a  large 
number  of  branches. 

The  brachial  plexus  communicates  with  the  cervical  sympathetic 
ganglia. 

The  second  thoracic  nerve  sends  a  branch,  the  intercoslohumeral , 
or  intcrcostobrachial  nerve,  directly  to  the  arm. 

The  primary  cords  of  the  plexus  are  formed  as  follows:  The  fifth 
and  sixth  nerves  form  the  first  cord;  the  seventh  constitutes  the.  second 
cord;  the  eighth  cervical  and  first  thoracic  nerves  form  the  third  cord. 
At  the  same  time  each  of  the  nerves  divides  into  ventral  and  dorsal 
trunks. 

The  secondary  cords  of  the  plexus  are  formed  as  follows:  The 


454  THE    NERVE    SYSTEM 

ventral  trunks  of  the  fifth,  sixth  and  seventh  nerves  form  the  lateral 
cord;  the  ventral  trunks  of  the  eighth  cervical  and  first  thoracic 
form  the  medial  cord;  the  dorsal  cord  is  formed  by  the  union  of  all  of 
the  dorsal  trunks  of  the  nerves  of  the  plexus.  These  cords  are 
lateral,  medial  and  dorsal  to  the  axillary  artery  and  from  this  rela- 
tion receive  their  names. 

The  branches  of  the  brachial  plexus  are  usually  described  under 
supraclavicular  and  infraclavicular  branches. 

The  supraclavicular  portion  (pars  supradavicularis)  represents  the 
branches  given  off  above  the  level  of  the  clavicle  and  these  are  an- 
terior and  posterior. 

The  Anterior  Branches. — Muscular  branches  to  the  mm.  scalenus 
anterior  and  longus  colli  (C.  5,  6,  7,  8). 

The  communicating  branch  to  the  phrenic  nerve  (C.  5). 

The  nerve  to  the  m.  subclavius  (C.  5,  6). 

The  posterior  branches  are  as  follows:  Branches  to  the  mm.  scaleni 
medius  and  posterior  (C.  5,  6,  7,  8). 

The  dorsal,  or  posterior  scapular  nerve  (n.  dorsalis  scapula)  is 
distributed  to  the  mm.  levator  scapula;,  rhomboidei  major  and  minor 
(C  5). 

The  long,  or  posterior  thoracic  nerve  (n.  thoracal  is  longus)  passes 
through  the  neck  into  the  axilla  to  the  m.  serratus  anterior  (C.  5, 

6,  7)- 

The  suprascapular  nerve  (n.  suprascapularis)  passes  from  the  neck 
to  the  superior  margin  of  the  scapula,  through  the  scapular  notch 
and  supplies  the  mm.  supraspinatus  and  infraspinatus  (C.  5,  6). 

The  infraclavicular  portion  (pars  infraclavicularis)  is  distributed 
to  the  shoulder,  ventral  part  of  the  thorax  and  the  extremity  proper. 
It  has  ventral  and  dorsal  branches.  Some  of  the*  ventral  branches 
are  from  the  lateral  cord  and  some  from  the  medial  cord.  The 
dorsal  branches  are  all  from  the  dorsal  cord. 

The  Ventral  Branches. — The  ventral,  or  anterior  thoracic  nerves,  are 
lateral  and  medial  and  arise  from  the  corresponding  cords.  The 
lateral  nerve  is  derived  from  the  fifth,  sixth  and  seventh  cervical 
nerves  and  the  medial  nerve  from  the  eighth  cervical  and  first  thor- 
acic nerves.     These  supply  the  mm.  pectorales  major  and  minor. 

The  musculocutaneous  nerve  (n.  musculocutancus)  is  derived  from 
the  lateral  cord  (C.  5,  6)  and  is  usually  accompanied  by  the  nerve 
to  the  m.  coracobrachialis  (C.  6,  7).  This  nerve  passes  through  the 
axilla  into  the  arm  (between  the  biceps  and  brachialis  muscles)  to 
elbow  where  it  continues  as  the  lateral  cutaneous  nerve  of  the  forearm, • 
this  divides  into  ventral  and  dorsal  branches.  The  ventral  branch  sup- 
plies the  skin  of  the  lateral  half  of  the  ventral  surface  of  the  forearm 
to  the  ball  of  the  thumb.  The  dorsal  branch  supplies  the  skin  of 
the  first  three-fourths  of  the  lateral  half  of  the  dorsal  surface  of  the 


THE    MEDIAN    NERVE 


455 


forearm.     The  only  muscular  branches  are  to  the  biceps  and  brachialis 
muscles. 

The  medial,  or  internal  cutaneous  nerve  (n.  cutaneous  antibrachii 
medialis),  is  derived  from  the  medial  cord  of  the  brachial  plexus 
(C.  8,  Th.  i).  It  passes  from  the  axilla  into  the  arm,  in  the  distal 
part  of  which  it  divides  into  ventral  and  ulnar  branches.  The  ventral 
branch  supplies  the  medial  half  of  the  ventral  surface  of  the  forearm 
to  the  wrist.  The  ulnar  branch  supplies  the  first  three-fourths  of 
the  medial  half  of  the  dorsal  surface  of  the  forearm. 


- 


Fig.  322. — Infracla 


■  portion  of  the  brachial  plexus  after  i 
toralis  major  and  minor  muscles. 


The  medial  cutaneous,  or  lesser  internal  cutaneous  nerve  of  the 
arm  is  derived  from  the  median  cord  of  the  brachial  plexus  (Th.  i). 
It  supplies  the  first  half  of  the  skin  of  the  medial  surface  of  the  arm. 

The  median  nerve  («.  medianus)  is  derived  from  the  medial 
(C.  8,  Th.  i)  and  lateral  (C.  5,  6,  7)  cords  by  two  heads.  It  passes 
from  the  axilla  through  the  arm  and  forearm  (between  the  superficial 
and  deep  muscles)  to  the  wrist  and  enters  the  palm. 

[ts  first  branches  are  given  off  in  the  forearm  to  the  elbow  joint. 
The  next  branches  are  muscular  for  the  mm.  pronator  teres,  flexor 
carpi    radialis,    palmaris    longus,    flexor   digitorum    sublimis.     The 


456  THE    XERVE    SYSTEM 

ventral,  or  volar  interosseous  nerve,  accompanies  the  ventral  in- 
terosseous artery  and  gives  off  muscular  branches  to  the  mm.  flexor 
longus  pollicis,  pronator  quadratus  and  lateral  half  of  the  flexor  digi- 
torum  sublimis;  it  gives  branches  to  the  radiocarpal  articulation. 

In  the  palm  the  median  nerve  supplies  the  skin. 

In  the  hand  it  gives  off  its  terminal  branches  which  are  muscular 
and  cutaneous.  The  muscular  branches  are  for  the  mm.  abductor 
pollicis  brevis,  the  opponens  pollicis  and  the  flexor  pollicis  brevis. 
The  cutaneous  branches  are  five  in  number;  the  first  three  supply  suc- 
cessively the  lateral  and  medial  sides  of  the  thumb  and  the  lateral 
side  of  the  index  finger;  the  other  two  branches  divide  into  two  each 
for  the  adjacent  sides  of  the  index  and  middle  and  the  middle  and 
ring  fingers,  respectively. 

The  ulnar  nerve  (nervus  ulnaris)  is  derived  from  the  medial  cord 
of  the  brachial  plexus  (C.  8,  Th.  1).  It  passes  from  the  axilla  through 
the  arm,  behind  the  medial  epicondyle  into  the  forearm  where  it 
lies  between  the  superficial  and  deep  muscles  of  the  ulnar  side.  It 
accompanies  the  ulnar  artery  into  the  palm  and  there  divides  into 
its  terminal  branches. 

Its  first  branches  are  in  the  forearm.  The  articular  branch  supplies 
the  elbow  joint.  The  muscular  branches  are  for  the  mm.  flexor  carpi 
ulnaris  and  medial  half  of  the  flexor  digitorum  profundus.  It  gives 
off  cutaneous  branches  that  extend  into  the  hand.  The  ventral  or 
palmar  cutaneous  branch  supplies  the  distal  third  of  the  ventral  sur- 
face of  the  forearm  (medial  half)  and  the  skin  of  the  hypothenar 
eminence.  The  dorsal  cutaneous  branch  supplies  the  skin  of  the 
distal  third  of  the  dorsal  surface  of  the  forearm  (medial  half)  and  the 
back  of  the  palm  and  also  gives  off  the  dorsal  digital  branches  for  the 
little  finger  and  the  adjacent  sides  of  little  and  ring  fingers. 

In  the  palm  the  ulnar  nerve  supplies  the  palmaris  brevis  muscle 
and  divides  into  a  superficial  and  a  deep  branch.  The  superficial 
branch  (cutaneous)  divides  into  two  digital  branches  for  the  medial 
side  of  the  little  finger  and  the  adjacent  sides  of  the  little  and  ring 
fingers.  The  deep  branch  supplies  the  mm.  flexor  brevis  and  abductor 
quinti  digiti,  opponens  quinti  digiti,  interossei,  lumbricales  (third 
and  fourth),  adductor  pollicis  and  flexor  pollicis  brevis  (deep  part). 

The  axillary,  or  circumflex  nerve  («.  axillaris),  is  derived  from  the 
dorsal  cord  (C.  5,  6).  It  is  large  and  passes  from  the  axilla,  winds 
around  the  surgical  neck  of  the  humerus  and  ends  by  giving  branches 
to  the  m.  deltoideus.  It  also  gives  muscular  branches  to  the  m.  teres 
minor,  articular  branches  to  the  shoulder  joint  and  a  large  cutaneous 
branch  to  the  skin  of  the  proximal  half  of  the  lateral  surface  of  the 
arm. 

The  radial,  or  musculospiral  nerve  (n.  radialis),  is  derived  from  all 
of  the  nerves  of  the  dorsal  cord.     It  leaves  the  axilla  and  passes  to 


THE    RADIAL    NERVE 


457 


the  bend  of  the  elbow  along  the  radial  groove  on  the  dorsal  surface 
of  the  humerus.  It  divides  into  superficial  and  deep  terminal 
branches.  In  its  course  through  the  arm  it  gives  off  a  number  of 
branches.     The  muscular  branches  are  distributed  to  the  mm.  triceps, 


Fig.  323- — Ne 


;  of  the  left  upper  extremity. 


anconeus,  brachialis,  brachioradialis,  extensor  carpi  radialis  longus 
and  at  times  the  brevis.  The  posterior  cutaneous  brachial  nerve  {the 
upper  internal  cutaneous  branch  of  the  musculospiral)  supplies  the 
skin  of  the  first  third  of  the  medial  surface  of  the  arm.     The  dorsal 


458  THE    NERVE    SYSTEM 

cutaneous  nerve  of  the  forearm  supplies  the  skin  of  the  dorsal  surface 
of  the  arm  (last  third)  and  of  the  first  two-thirds  of  the  forearm. 

The  terminal  branches  are  the  superficial  and  deep  rami.  The 
superficial  ramus,  or  old  radial  nerve  arises  near  the  elbow,  passes 
along  the  lateral  part  of  the  forearm  and  in  the  lower  third  it  passes 
to  the  dorsal  surface  to  end  in  branches  that  supply  the  skin  of  the 
back  of  the  wrist  and  some  of  the  fingers.  Its  digital  branches  are 
five  in  number;  the  first  three  supply  both  sides  of  the  thumb  and  the 
radial  side  of  the  index  finger.  The  other  two  branches  divide  into 
two  each  for  the  contiguous  sides  of  the  index  and  middle  and  the 
middle  and  ring  fingers. 

The  deep  ramus,  or  posterior  interosseous  nerve,  supplies  the 
muscles  of  the  forearm  and  the  carpal  articulations.  The  nerve  lies 
between  the  superficial  and  deep  muscles  and  supplies  the  following: 
mm.  carpi  radialis  brevis,  supinator,  extensores  digitorum  communis, 
digiti  quinti  proprius,  carpi  ulnaris,  the  abductor  pollicis  longus, 
extensores  pollicis  longus  and  brevis  and  extensor  indicis  proprius. 

The  first,  or  short  subscapular  nerve  in.  subscapularis),  is  derived 
from  the  fifth  and  sixth  cervical  nerves  (dorsal  cord)  and  supplies 
the  subscapularis  muscle. 

The  second,  or  lower  subscapular  nerve,  has  the  same  origin  and 
passes  to  the  teres  major  and  subscapularis  muscles. 

The  thoracodorsal,  or  long  subscapular,  nerve  arises  from  the  sixth 
and  seventh  and  eighth  cervical  nerves  (dorsal  cord).  It  supplies 
the  latissimus  dorsi  muscle. 

THE  LUMBOSACRAL  PLEXUS  (PLEXUS  LUMBOSACRALIS) 

The  lumbosacral  plexus  is  formed  by  the  ventral  rami  of  the  five 
lumbar,  the  five  sacral  and  one  coccygeal  nerves.  It  is  usually 
divided  into  lumbar,  sacral  and  pudendal  plexuses. 

The  lumbar  plexus  is  formed  by  the  ventral  rami  of  the  first,  second, 
third  and  a  branch  of  the  fourth  lumbar  nerves.  It  is  formed  within 
the  substance  of  the  psoas  muscles  and  also  divides  into  its  branches 
here.  The  first  two  nerves  divide  into  superior  and  inferior  branches. 
The  superior  branch  of  the  first  lumbar  nerve  divides  into  the  ilio- 
hypogastric and  ilioinguinal  nerves.  The  inferior  branch  of  the  first 
and  the  superior  branch  of  the  second  nerve  form  the  genitofemoral 
nerve.  The  inferior  branch  of  the  second,  the  whole  third  and  the 
branch  of  the  fourth  lumbar  nerves  divide  into  smaller  ventral  and 
larger  dorsal  divisions.  The  ventral  divisions  form  the  obturator 
nerve;  the  dorsal  divisions  form  the  femoral,  and  lateral,  or  external 
cutaneous,  or  anterior  crural  nerves.  In  addition  independent 
muscular  branches  are  given  off.     The  branches  are  as  follows: 

Muscular  branches  pass  to  the  m.  quadrat  us  lumborum  (L.i,  2,3,4), 
psoas  major  (L.  2,  3),  psoas  minor  (L.  1). 


THE    LUMBAR    PLEXUS 


459 


The  iliohypogastric  nerve  (w.  iliohypogastrics)  passes  into  the  loin 
along  the  crest  of  the  ilium  into  the  groin  and  gives  off  muscular 
branches  (to  the  muscles  of  the  abdominal  wall)  and  the  lateral  and 
ventral  cutaneous   branches.     These   cutaneous   branches   supply   the 


Lai.  cutaneous  branch  of 

ilioliypogastric 
Genitofemoral 
Ilioinguinal 

Muscular  branches 
to  the  Mop, 
External  spermatic  nerve** 
tat.  femoral  cut. 
Lumbj-: 


Tibial 

ifu:-f 

long  head  of 

bieeps  and 

semitendinosus 

inter  r.us 
Posterior  femoral  cutaneous  nave 

Medial  infer,  cluneal 
Perineal  nerve-rdors.  nerve  of  penis 
Infer,    hemorrhoidal 


Muse,  branches  t, 

Fig.  324- 


■  d  axcygeui 

-Lumbosacral  pies 


{.After  P.  Eisler.) 


skin  of  the  superolateral  part  of  the  buttock  and  the  ventral  abdom- 
inal wall. 

The  ilioinguinal  nerve  (n.  ilutinguinalis)  passes  along  the  iliac 
fossa  to  the  external  abdominal  ring  and  supplies  branches  to  the 
skin  of  the  pubic  region,  scrotum  and  root  of  the  penis  (or  mons 
veneris  and  labia  majora)  and  the  superomedial  portion  of  the  thigh. 


460 


THE    NERVE    SYSTEM 


-lateral  Cutaneous M 


'^rme^a/e  CuHuiems  ^ 4 


Superficial  Perorrea!  /V— 


Fig.  325. —  Nerves  of  the  ventral  part  of  the  right  lower  extremity, 


THE    SACRAL    PLEXUS  461 

The  genitofemoral  nerve  (n.  genilofemoralis)  passes  across  the 
iliac  fossa  and  gives  off  an  external  spermatic  branch  that  supplies 
a  part  of  the  scrotum  and  thigh;  the  remainder  passes  into  the  thigh 
along  side  of  the  femoral  artery  and  supplies  the  skin  of  the  ventral 
and  proximal  part  of  the  thigh. 

The  lateral  cutaneous  nerve  (n.  cutaneous  femoralis  lateralis) 
passes  into  the  thigh  and  supplies  the  skin  of  the  ventrolateral  and 
lateral  aspects  of  the  thigh  and  buttocks. 

The  obturator  nerve  («.  obtnratorius)  (L.  2,  3,  4)  passes  into  the 
thigh  through  the  obturator  groove.  Its  ventral,  or  superficial 
branch  supplies  muscular  branches  to  the  adductores  longus  and 
brevis,  the  gracilis  and  occasionally  the  pectineus;  an  articular 
branch  to  the  hip  joint;  a  cutaneous  branch  to  the  skin  of  the  medial 
surface  of  the  thigh  (distal  two-thirds);  a  branch  to  the  femoral 
artery.  The  dorsal,  or  deep  branches  pass  into  the  thigh  and  give 
muscular  branches  to  the  obturator  externus,  adductores  magnus 
and  brevis;  an  articular  branch  to  the  knee  joint. 

The  femoral,  or  anterior  crural,  nerve  («.  femoralis)  is  a  large 
nerve  derived  from  the  second,  third  and  fourth  lumbar  nerves.  It 
passes  through  the  iliac  fossa  and  into  the  thigh  at  the  side  of  the 
femoral  sheath  and  in  the  femoral  triangle  gives  off  a  number  of 
branches.  The  muscular  branches  are  distributed  to  the  mm.  pec- 
tineus, sartorius,  rectus  femoris,  vasti  lateralis,  medialis  and  inter- 
medins; articular  branches  to  the  hip  and  knee  joints;  cutaneous 
branches,  the  intermediate  and  medial  cutaneous  branches,  that  supply 
the  skin  of  the  ventral  part  of  the  thigh  to  the  knee. 

The  saphenous  nerve  (n.  saphenus)  is  the  terminal  part  of  the 
femoral  nerve.  It  passes  into  the  leg  and  supplies  the  medial  side 
of  the  knee  and  patellar  regions,  the  medial  side  of  the  leg  and  foot. 

THE  SACRAL  PLEXUS  (PLEXUS  SACRALIS) 

The  sacral  plexus  is  formed  by  the  remainder  of  the  fourth,  all 
of  the  fifth  lumbar  and  all  of  the  first  and  part  of  the  second  and  third 
sacral  nerves.  The  fourth  and  fifth  lumbar  and  the  first  and  second 
sacral  nerves  divide  into  ventral  and  dorsal  divisions.  The  third 
sacral  nerve  divides  into  superior  and  inferior  divisions,  the  latter 
forming  the  pudendal  plexus.  The  ventral  divisions  of  the  fourth 
and  fifth  lumbar  and  first,  second  and  the  superior  part  of  the 
third  sacral  nerves  form  the  tibial  nerve.  The  dorsal  divisions  form 
the  common  peroneal  nerve.  The  branches  of  distribution  are 
dorsal  and  ventral. 

The  sciatic  nerve  is  really  the  tibial  and  common  peroneal  nerves 
with  extra  nerves  for  the  hamstring  muscles.  This  large  nerve 
passes  through  the  greater  sciatic  foramen  into  the  buttock  and  then 
into  the  thigh  where  it  divides  into  the  tibial  and  common  peroneal 


462 


THE    NERVE    SYSTEM 


•Super/or  GJuteal  M 


Pudendal  N 
Small  Sciatic  N-  %. 


Common  Peroneal  N. 


oneal  Ana5.br. 


PlonTar  Cutaneous  M- 


Fig.  326. — Nerves  of  the  dorsal  part  of  the  right  lower  extremity. 


THE    PLANTAR    NERVES  463 

nerves  at  almost  any  level.  In  its  course  the  sciatic  nerve  gives 
branches  to  the  mm.  biceps,  semitendinosus,  semimembranosus  and 
the  adductor  magnus. 

Collateral  branches  of  the  sacral  plexus  are  given  off  as  follows: 
muscular  branches  to  the  mm.  quadratus  femoris,  obturator  internus, 
gemelli  superior  and  inferior,  pyriformis,  glutei  maximus,  medius, 
minimus;  articular  branches  to  the  hip  joint. 

The  tibial,  or  internal  popliteal,  nerve  (».  tibialis)  is  derived  from 
the  fourth  and  fifth  lumbar  and  first  three  sacral  nerves.  It  is  a 
part  of  the  sciatic  nerve  to  various  levels  of  the  thigh  but  is  usually 
individual  before  the  popliteal  space  is  reached.  It  continues 
through  the  back  of  the  leg  to  the  back  of  the  ankle  and  passes  into 
the  foot  where  it  divides  into  medial  and  lateral  plantar  nerves. 

In  the  popliteal  space  it  gives  branches  to  the  knee  and  proximal 
tibiofibular  joints;  muscular  branches  to  the  mm.  plantaris,  gastroc- 
nemius (both  heads)  popliteus;  the  medial  cutaneous  sural  nerve 
(tibial  communicating  nerve)  is  joined  by  the  peroneal  anastomotic 
branch  of  the  common  peroneal  nerve  and  these  form  the  sural  nerve 
that  accompanies  the  small  saphenous  vein  and  supplies  the  skin  of 
the  lateral  and  back  parts  of  the  calf,  ankle  and  heel  and  the  side  of 
the  foot;  it  also  gives  branches  to  the  ankle  and  tarsal  joints.  In 
the  back  of  the  leg  the  tibial  nerve  distributes  muscular  branches  to 
the  mm.  tibialis  posterior,  flexor  digitorum  longus,  flexor  hallucis 
longus;  cutaneous  branches  to  the  skin  of  the  medial  malleolus  and 
the  heel  and  posterior  part  of  the  sole  of  the  foot;  articular  branches 
to  the  ankle  joint. 

The  medial  plantar  nerve  is  the  larger  of  the  two  terminal  branches 
and  accompanies  the  medial  plantar  artery.  Its  collateral  branches 
are  muscular  to  the  mm.  abductor  hallucis  and  flexor  digitorum 
brevis;  cutaneous  to  the  skin  of  the  medial  part  of  the  sole  of  the  foot; 
articular  branches  to  the  tarsal  and  metatarsal  joints. 

The  common  digital  plantar  nerves  are  four  in  number.  The  first 
(medial)  supplies  the  m.  flexor  hallucis  brevis,  and  the  skin  of  the 
medial  side  of  the  foot  and  great  toe.  The  second  supplies  the  first 
lumbricale  muscle  and  then  divides  into  two  proper  digital  nerves 
for  the  adjacent  sides  of  the  great  and  second  toes.  The  third  and 
fourth  divide  into  proper  digital  branches  for  the  skin  of  the  adjacent 
sides  of  the  second  and  third  and  the  third  and  fourth  toes. 

The  lateral  plantar  nerve  accompanies  the  lateral  plantar  artery. 
It  distributes  collateral  branches  to  the  quadratus  plantae  and  ab- 
ductor digiti  cjuinti  muscles;  cutaneous  branches  to  the  sides  of  the 
foot.  Its  terminal  branches  are  the  superficial  and  deep  rami.  The 
superficial  ramus  [lateral  branch)  supplies  the  flexor  digiti  quinti 
1)K  \  is  and  the  two  interossei  of  the  fourth  space  and  the  skin  of  the 
sole  and  of  the  lateral  surface  of  the  little  toe.     The  medial  branch 


464 


THE    NERVE    SYSTEM 


divides  into  proper  digital  nerves  for  the  adjacent  sides  of  the  little 
and  fourth  toes.  The  deep  ramies  gives  off  muscular  branches  to  the 
interossei  muscles  (except  those  of  the  fourth  space)  to  the  adductor 
hallucis  and  the  three  lateral  lumbricale  muscles;  articular  branches 
to  the  tarsal  and  metatarsal  joints. 

The  common  peroneal,  or  external  popliteal  nerve  (n.  peroneus 
communis),  passes  through  the  popliteal  space  to  the  back  of  the 
head  of  the  fibula.  It  gives  off  collateral  branches  as  follows:  a  mus- 
cular branch  to  the  short  head  of  the  biceps;  articular  to  the  knee 


Fir,.    327. — The  plantar 


joint;  two  cutaneous  branches,  the  lateral  sural  branch  and  the  anasto- 
motic branch.  The  lateral  sural  branch  arises  in  the  popliteal  space 
and  supplies  the  skin  of  the  lateral  surface  and  back  of  the  leg  in 
the  first  two-thirds.  The  peroneal  anastomotic  nerve  (fibular  com- 
municating nerve)  joins  the  corresponding  branch  of  the  tibial  nerve 
the  distribution  of  which  has  been  given. 

The  terminal  branches  of  the  common  peroneal  nerve  are  the 
following: 

The  tibial  recurrent  nerve  supplies  the  proximal  part  of  the  tibialis 
anterior  muscle,  the  knee  and  tibiofibular  joints. 


THE    PUDENDAL   PLEXUS  465 

The  deep  peroneal,  or  anterior  tibial,  nerve  (».  peroneus  profundus) 
passes  to  the  front  of  the  leg  and  accompanies  the  anterior  tibial 
artery  to  the  dorsum  of  the  foot.  In  the  leg  it  gives  off  muscular 
branches  to  the  mm.  tibialis  anterior,  extensores  hallucis  longus, 
digitorum  longus  and  peroneus  tertius;  a  branch  to  the  ankle  joint. 
Its  terminal  branches  in  the  foot  are  medial  and  lateral.  The  medial 
branch  that  accompanies  the  dorsalis  pedis  artery  and  supplies  the 
first  dorsal  interosseous  muscle  and  the  skin  of  the  medial  side  of 
the  great  toe  and  the  adjacent  sides  of  the  great  and  second  toes, 
also  the  adjacent  joints.  The  lateral  branch  gives  off  muscular 
branches  to  the  extensor  digitorum  brevis  muscle,  the  tarsal  and 
metatarsal  joints  and  branches  (sensor  probably)  to  the  second  and 
third  dorsal  interossei. 

The  superficial  peroneal,  or  musculocutaneous  nerve  is  the  last 
branch  of  the  common  peroneal  nerve  and  lies  between  the  peroneus 
longus  and  extensor  digitorum  longus  muscles.  It  gives  collateral 
muscular  branches  to  the  peronei  longus  and  brevis  muscles  and 
divides  into  dorsal  medial  and  intermediate  cutaneous  nerves.  The 
former  ultimately  divides  into  two  branches  that  supply  the  adjacent 
sides  of  the  second  and  third  toes.  The  latter  divides  into  two 
branches  each  of  which  divides  into  two  for  the  supply  of  the  skin 
of  the  adjacent  sides  of  the  third  and  fourth  and  the  fourth  and 
fifth  toes. 

THE  PUDENDAL  PLEXUS  (PLEXUS  PUDENDUSl 

The  pudendal  plexus  is  formed  by  fibers  from  the  first  three  sacral 
nerves  and  by  the  anterior  rami  of  the  fourth  and  fifth  sacral  and 
first  coccygeal  nerves.  It  receives  gray  rami  communicantes  from 
the  sympathetic  system.     It  gives  rise  to  a  number  of  branches. 

The  posterior  cutaneous  nerve  of  the  thigh  (small  sciatic  nerve)  is 
derived  from  the  first  three  sacral  nerves.  It  is  a  cutaneous  nerve 
and  its  branches  are  as  follows:  Perineal  branches  supply  the  scrotum 
and  root  of  the  penis,  or  the  labium  majus  and  clitoris  and  part  of 
the  skin  of  the  perineum.  The  inferior  gluteal  branches  supply  the 
skin  of  the  lower  half  of  the  buttock  and  back  of  the  thigh.  The 
perforating  cutaneous  nerve  supplies  the  skin  of  the  lower  part  of  the 
buttock  and  the  medial  surface  of  the  nates. 

The  muscular  branches  pass  to  the  levator  ani,  coccygeus  and  ex- 
ternal sphincter  muscles.  The  nerve  to  the  external  sphincter  mus- 
cle also  supplies  cutaneous  branches  to  the  skin  of  the  ischiorectal 
fossa  and  the  fold  of  the  nates  behind  the  anus. 

The  anococcygeal  nerve  is  derived  from  a  plexus  formed  by  the 
remainder  of  the  fourth  and  fifth  sacral  and  coccygeal  nerves;  it 
supplies  the  skin  of  the  coccyx  region  and  that  back  of  the  anus. 

The  pudendal,  or  pudic  nerve  arises  in  the  pelvis  from  the  second, 


466  THE    NERVE    SYSTEM 

third  and  fourth  sacral  nerves.  It  passes  to  the  buttock  through 
the  greater  sacrosciatic  foramen  and  in  the  ischiorectal  fossa  divides 
into  its  terminal  branches.  The  inferior  hemorrhoidal  nerve  accom- 
panies the  inferior  hemorrhoidal  artery  and  gives  off  muscular 
branches  to  the  external  sphincter  ani  muscle;  cutaneous  branches  to 
the  skin  around  the  anus;  communicating  nerves  to  the  surrounding 
nerves.  The  perineal  nerve  consists  of  superficial  and  deep  portions. 
The  superficial  portion  is  cutaneous  and  as  its  lateral  and  medial 
divisions  supplies  the  skin  of  the  scrotum,  or  labium  majus.  The 
deep  branch  gives  off  muscular  branches  to  the  anterior  portion  of 
the  mm.  levator  ani,  and  external  sphincter,  the  transversus  perinei 
(superficialis  et  profundus),  ischiocavernosus  (or  sphincter  vaginas), 
ischiobulbosus,  sphincter  urethra;  membranaceae.  It  also  supplies 
the  erectile  tissue  of  the  bulb  and  corpus  cavernosum  and  the  mucosa 
of  the  urethra  as  far  as  the  glans. 

The  dorsal  nerve  of  the  penis,  or  clitoris  accompanies  the  internal 
pudendal  artery.  It  passes  under  the  pubic  arch  and  along  the 
dorsum  of  the  penis  or  clitoris.  It  sends  branches  into  and  around 
the  corpus  cavernosum. 

THE  SYMPATHETIC  NERVE  SYSTEM 

The  sympathetic  nerve  system  (systema  nervorum  sympathicum), 
although  seemingly  an  independent  structure,  is  intimately  con- 
nected with  the  cerebrospinal  system.  Owing  to  its  peculiar  ar- 
rangement and  appearance  it  is  called  the  ganglionatcd  cord  and  ex- 
tends from  the  base  of  the  skull  to  the  coccyx.  It  rearranges  and 
distributes  fibers  of  the  cerebrospinal  system  to  the  viscera;  it  trans- 
mits sensor  impulses  from  the  viscera  to  the  cerebrospinal  system; 
it  sends  motor  fibers  to  vessels  and  organs  through  the  cerebrospinal 
nerves. 

This  system  consists  of  a  series  of  central  ganglia,  collateral  ganglia 
and  terminal  ganglia.  The  central  ganglia  (ganglia  trunci  sympa- 
thies) are  arranged  in  pairs  on  each  side  of  the  midline  from  the 
base  of  the  skull  to  the  coccyx;  they  are  connected  with  one  another 
up  and  down  (on  the  same  side  only).  The  fibers  are  gray  in  color 
and  constitute  the  gray  rami  communicantes;  these  are  connecting 
and  distributor^-  in  function. 

Each  ganglion  consists  of  a  variable  number  of  large,  multipolar 
nerve  cells  surrounded  by  a  capsule  of  white  fibrous  tissue.  In  addi- 
tion neuroglia,  myelinated  and  amyelinated  nerve  fibers  are  present. 
Each  cell  possesses  a  main  process,  the  axone,  that  may  be  associative 
in  function,  or  may  pass  to  the  cerebrospinal  system  as  the  gray 
ramus  communicans,  or  it  may  pass  to  the  periphery,  or  to  ganglia 
farther  out.  The  dendrites  are  usually  numerous  and  serve  an 
associative  function   in   the   immediate   neighborhood.     The   white 


THE    SYMPATHETIC    NERVE    SYSTEM  467 

rami  communicantes  are  from  two  main  sections  of  the  spinal  cord, 
the  thoracicolumbar  (from  the  second  thoracic  to  the  second  lumbar 
nerve  levels)  and  the  pelvic,  or  sacral  (from  the  second  to  the  fourth 
sacral  nerve  levels).  Both  ventral  and  dorsal  roots  of  the  spinal 
nerves  are  concerned. 

The  small  fibers  {white  rami  communicantes)  from  the  ventral 
roots  of  the  spinal  nerves  may  end  in  the  central  ganglia  of  that 
level;  they  may  pass  through  that  ganglion  and  up  or  down  to 
another  one  of  the  central  ganglia;  they  may  pass  through  the 
central  ganglion  and  terminate  in  a  collateral  ganglion.  All  of  these 
fibers  are  the  splanchnic  efferent  fibers.  The  sensor  fibers  are  the 
splanchnic  afferent*;  and  the  cells  lie  in  the  dorsal  root. 

Although  in  early  fetal  life  there  are  as  many  pairs  of  ganglia  as  vertebral  seg- 
ments, at  birth  this  condition  does  not  prevail.  The  central  ganglia  are  ar- 
ranged as  follows: 

Cervical 3  pairs.  s 

Thoracic 10  to  12  pairs. 

Lumbar 4  pairs. 

Sacra! 4  to  5  pairs. 

Coccygeal  a  single  one. 
These  communicate  with  one  another  up  and  down. 

Fibers  from  the  spinal  nerves  that  pass  to  the  sympathetic  ganglia  are  wkite 
and  constitute  the  white  rami  communicantes.  Those  from  the  sympathetic 
system  to  the  spinal  cord  are  gray  and  constitute  the  gray  rami  communicantes. 
These  are  the  communicating  fibers. 

I  In  libers  of  distribution  are  chiefly  gray  and  pass  from  the  various  sympathetic 
ganglia  to  vessels  and  organs  of  the  thoracic  and  abdominal  cavities,  that  is,  the 
muscles  and  epithelium  thereof  representing  both  motor  and  sensor  fibers. 

The  collateral  ganglia,  or  ganglionated  plexuses  are  the  cardiac, 
solar  and  hypogastric  plexuses. 

The  terminal  ganglia  are  in  the  various  organs,  as  in  the  plexuses 
of  Auerback  and  Meissner  of  the  gastrointestinal  tract. 

The  cervical  portion  (pars  cephalica  el  cervical  is)  of  the  central  sys- 
tem comprises  three  pairs  of  ganglia,  the  superior,  middle  and  in- 
ferior cervical  ganglia.  No  white  rami  communicantes  are  found 
here. 

The  branches  of  these  ganglia  are  either  central  communicating 
branches  for  the  other  nerves,  or  peripheral  branches  that  pass 
directly,  or  through  plexuses  to  the  viscera  and  vessels  of  the  head, 
neck  and  thorax. 

The  superior  cervical  ganglia  (ganglia  cervicalcs  superiores)  are  the 
largest;  each  lies  opposite  the  second  and  third  cervical  vertebra?. 
Each  is  broad,  fiat  and  spindle-shaped,  of  a  reddish  color  and  repre- 
sents a  fusion  of  the  first  four  conical  ganglia.  From  its  superior 
(cephalic)  end  a  branch  ascends  along  the  internal  carotid  artery 
and  in  the  skull  its  two  branches  form  the  internal  carotid  and  cavern- 


468 


THE    NERVE    SYSTEM 


ous  plexuses.  The  carotid  plexus  communicates  with  the  semilunar 
(Gasserian)  and  sphenopalatine  ganglia  and  the  abducens  and  glosso- 
pharyngeal nerves.  The  cavernous  plexus,  in  the  cavernous  sinus, 
communicates  with  the  oculomotor,  trochlear,  the  ophthalmic  divi- 
sion of  the  trigeminus  and  abducens  nerves  and  the  ciliary  ganglion. 
Other  branches  of  these  plexuses  follow  the  anterior,  middle  cerebral 
and  ophthalmic  arteries. 


Fig.  328. — Diagram  of  the  sympathetic  ganglia  and  their  connections 


Other  branches  of  the  superior  cervical  ganglion  communicate 
with  the  middle  ganglion,  the  first  four  cervical  nerves  (ventral 
roots)  vagal,  glossopharyngeal  (forming  the  pharyngeal  plexus),  and 
hypoglossal  nerves,  while  others  pass  to  the  larynx,  pharynx  and 
heart;  the  latter  form  the  superficial  cardiac  nerve,  the  right  one  join- 
ing the  deep  cardiac  plexus  and  the  left  the  superior  cardiac  plexus. 

The  middle  cervical  ganglia  {ganglia  cervicales  mediates)  are  the 
smallest  and  lie  in  front  of  the  sixth  cervical  vertebra  and  represent 
the  fifth  and  sixth  ganglia  fused. 

Each  sends  branches,  gray  rami  communicantes,  to  the  fifth  and 


THE    CENTRAL    SVMPATHETHIC    GANGLIA  469 

sixth  cervical  nerves  and  to  the  subclavian  artery.  Peripheral 
branches  pass  to  the  thyreoid  gland  and  heart,  as  the  middle  cardiac 
nerve  to  the  deep  cardiac  plexus.  This  ganglion  may  be  absent  and 
when  this  occurs  these  branches  arise  direct  from  the  cord  in  that 
region. 

The  inferior  cervical  ganglia  {ganglia  cervicales  inferiores)  lie  upon 
a  level  with  the  seventh  cervical  vertebra  and  are  irregular  in  shape. 
Each  usually  represents  a  fusion  of  the  seventh  cervical  and  the  first 
thoracic  ganglia  and  each  sends  branches,  gray  rami,  to  the  seventh 
and  eighth  cervical  nerves  and  the  subclavian  artery;  it  also  gives 
off  the  inferior  cardiac  nerve  that  joins  the  deep  cardiac  plexus. 
Other  branches  follow  the  vertebral  artery  into  the  skull  and  these 
continue  along  the  cerebral  and  cerebellar  arteries. 

The  thoracic  ganglia  (pars  thoracalis)  are  ten  to  twelve  pairs  in 
number.  They  rest  against  the  heads  of  the  ribs,  behind  the  pleura. 
The  first  often  fuses  with  the  last  cervical  and  the  eleventh  and 
twelfth  are  usually  fused.  All  of  the  spinal  thoracic  nerves  (except 
the  first)  send  white  rami  to  these  ganglia.  Branches  from  the  first 
five  pairs  of  thoracic  ganglia  go  to  the  aorta  and  its  branches  and 
from  the  second,  third  and  fourth  others  go  to  the  posterior  pulmon- 
ary plexus.  From  the  lower  ganglia  branches  go  to  the  aorta  and 
others  form  the  splanchnic  nerves. 

The  great  splanchnic  nerve  (n.  splanchnicus  major),  on  each  side, 
is  formed  by  branches  from  the  fifth,  sixth,  seventh,  eighth  and 
ninth  ganglia  and  is  whitish  in  color.  It  passes  through  the  crus  of 
the  diaphragm  and  joins  the  celiac  ganglion  of  the  solar  plexus  and 
ultimately  the  renal  and  adrenal  plexuses.  In  the  thorax  branches 
pass  to  the  aorta  and  esophagus. 

The  lesser  splanchnic  nerve  (n.  splanchnicus  minor)  is  formed  by 
branches  from  the  ninth  and  tenth  ganglia,  passes  through  the  dia- 
phragm to  join  the  aorticorenal  ganglion  of  the  solar  plexus. 

The  least  splanchnic  nerve  (n.  splanchnicus  imus)  is  made  up  of 
fibers  from  the  eleventh  thoracic  ganglion,  pierces  the  diaphragm 
and  ends  in  the  renal  plexus. 

The  lumbar  ganglia  are  usually  four  in  number  upon  each  side, 
small  and  placed  near  the  midline.  They  receive  white  rami  from 
the  first  two  lumbar  nerves.  They  send  branches  to  the  lumbar 
nerves  and  to  the  abdominal  aorta  and  aortic  plexus. 

The  sacral  ganglia  (pars  pclviua)  are  four  or  five  in  number  on 
each  side  on  the  front  of  the  sacrum;  branches  pass  to  the  sacral 
nerves.  Some  of  the  sacral  nerves  send  branches  through  the  gang- 
lia. Other  branches  pass  to  the  pelvic  plexus  and  the  vessels  and 
pelvic  organs,  as  bladder,  rectum,  uterus  (motor  and  inhibitor 
fibers)  prostate  (secretor  fibers)  and  vasodilatator  fibers  to  the  geni- 
tal organs. 


47°  THE    NERVE    SYSTEM 

In  front  of  the  coccyx  the  two  cords  join  to  form  a  single  coccygeal 
ganglion,  or  ganglion  impar. 


The  cardiac  plexus  (plexus  cardiac  us)  comprises  the  superficial  and 
deep  portions  and  lies  at  the  base  of  the  heart.  The  superficial  plexus, 
under  the  arch  of  the  aorta,  is  formed  by  the  left  superior  cardiac 
nerve,  the  left  inferior  cervical  cardiac,  a  branch  from  the  vagus  and 
some  fibers  from  the  deep  plexus.  The  ganglion  of  Wrisberg  may 
be  present.  From  this  plexus  branches  pass  to  the  left  half  of  the 
deep  plexus  and  to  the  anterior  coronary  and  left  anterior  pulmonary 
plexuses. 

The  deep  portion  (plexus  cardiacus  profundus)  is  situated  in  front 
of  the  tracheal  bifurcation.  It  is  the  larger  and  is  formed  by  the 
cardiac  branches  of  the  cervical  ganglia  (except  left  superior) 
branches  of  the  recurrent  laryngeal  and  vagal  nerves.  Branches 
pass  to  the  anterior  and  posterior  coronary  plexuses.  The  left  cor- 
onary plexus  sends  branches  to  the  left  atrium  and  ventricle  and  the 
right  coronary  plexus  to  the  right  atrium  and  ventricle.  Branches 
also  pass  to  the  pulmonary  plexuses. 

The  pulmonary  plexuses  (plexus  puhnonaJes)  are  ventral  and 
dorsal.  The  ventral  plexus  on  each  side  lies  upon  the  structures  at 
the  ventral  part  of  the  root  of  the  lung,  which  structures  it  supplies. 
Each  receives  fibers  from  the  deep  cardiac  plexus  and  the  left  from 
the  superficial  cardiac  plexus  also.  The  dorsal  plexus  lies  behind 
the  root  of  the  lung  and  is  formed  by  branches  from  the  second, 
third  and  fourth  thoracic  sympathetic  ganglia,  but  chiefly  branches 
from  the  vagal  nerve.  Branches  therefrom  pass  along  the  vessels 
and  bronchi. 

The  esophageal  plexuses  (plexus  esophagei)  are  ventral  and  dorsal 
and  are  formed,  chiefly,  by  the  vagal  nerves  through  the  pulmonary 
plexuses;  branches  from  these  plexuses  pass  into  the  esophagus  and 
pericardium.  The  lower  part  of  the  esophagus  also  receives  fibers 
from  the  greater  splanchnic  nerve. 

The  solar,  or  celiac  plexus  (plexus  celiacus)  is  a  great  network  of 
sympathetic  nerves  and  ganglia  situated  in  front  (.ventrad)  of  the 
aorta  and  crura  of  the  diaphragm  and  behind  the  pancreas;  it  is 
in  relation  with  the  celiac  axis  and  superior  mesenteric  arteries.  To 
this  plexus  pass  all  of  the  splanchnic  nerves  and  branches  from  the 
right  vagus.  From  it  pass  branches  to  the  viscera  of  the  abdomen 
and  along  the  branches  of  the  aorta.  It  consists  of  the  celiac  plexus 
and  two  main  ganglionic  masses,  the  celiac  ganglia.  This  plexus  is 
connected  with  the  renal,  diaphragmatic,  adrenal,  aortic  and  supe- 
rior mesenteric  plexuses  and  others  lower  down. 

The  most  important  ganglia  are  the  celiac;  these  are  the  largest 


THE    ABDOMINAL    SYMPATHETIC    PLEXUSES  47 1 

in  the  body.  Each  is  large  and  irregular,  situated  in  front  of  the 
cms  of  the  diaphragm  and  consists  of  a  collection  of  smaller  ganglia. 
The  upper  end  of  each  receives  the  great  splanchnic  nerve  while 
the  lower  part  constitutes  the  aorticorenal  ganglion  that  receives  the 
lesser  splanchnic  nerves. 

The  solar  plexus  gives  rise  to  a  number  of  plexuses. 

1.  The  phrenic  plexuses  receive  branches  from  the  phrenic  nerves. 
The  right  is  the  larger  and  may  possess  a  ganglion.  From  each 
branches  pass  to  the  diaphragm  and  (on  the  right  side)  to  the  inferior 
vena  cava  and  to  the  suprarenal  and  hepatic  plexuses. 

2.  The  coronary  plexus  sends  branches  to  the  esophagus  and  along 
the  lesser  curvature  of  the  stomach  that  join  branches  of  the  vagus. 

3.  The  splenic  plexus,  chiefly  from  the  left  celiac  ganglion,  accom- 
panies the  splenic  artery  to  the  spleen,  likewise  giving  branches  to 
the  pancreas  and  the  greater  curvature  of  the  stomach.  Branches 
of  the  right  vagus  join  the  plexus. 

4.  The  hepatic  plexus  is  the  largest  and  receives  branches  from  the 
left  vagal  and  phrenic  nerves.  Its  branches  go  to  the  liver  and 
pyloric  portion  of  the  stomach,  duodenum,  pancreas,  greater  curva- 
ture of  the  stomach  and  to  the  gall-bladder.  These  branches  form 
plexuses  along  the  arteries  and  take  their  names  therefrom. 

5.  The  suprarenal  plexus,  on  each  side,  contains  a  ganglion  at  the 
junction  of  branches  of  the  celiac  ganglion,  great  splanchnic  and 
phrenic  nerves  and  renal  plexus  that  form  this  plexus.  It  sends 
branches  to  the  adrenal,  or  suprarenal  glands. 

6.  The  superior  mesenteric  plexus  surrounds  the  superior  mesen- 
teric artery  and  receives  branches  from  the  right  vagal  nerve,  the 
celiac  and  aorticorenal  ganglia.  As  it  passes  into  the  mesentery  it 
gives  rise  to  subplcxuses  that  follow  the  branches  of  this  artery,  as 
the  pancreatic,  intestinal,  iliocolic,  right  colic  and  middle  colic.  It  has 
a  ganglion  at  the  root  of  the  artery. 

7.  The  renal  plexuses  consist  of  branches  of  the  solar  plexus, 
aorticorenal,  adrenal  and  aortic  plexuses  and  the  least  splanchnic 
nerves;  branches  pass  to  the  kidneys  and  to  the  spermatic  plexuses. 

8.  (a)  The  spermatic  plexuses  are  formed  by  branches  from  the 
renal  and  aortic  plexuses;  branches  pass  to  the  testes. 

(b)  The  ovarian  plexuses  are  formed  in  the  same  manner  and  send 
branches  to  the  ovaries,  oviducts  and  borders  of  the  uterus.  They 
communicate  with  the  uterine  plexus. 

9.  The  aortic  plexus  is  situated  upon  the  front  and  sides  of  the 
abdominal  aorta  between  the  superior  and  inferior  mesenteric 
arteries.  It  is  made  up  of  branches  from  the  solar  plexus  and  the 
lumbar  sympathetic  ganglia.  It  distributes  branches  to  the  sper- 
matic, inferior  mesenteric,  suprarenal,  renal,  and  hypogastric  plexuses 
and  to  the  inferior  vena  cava. 


472 


THE    NERVE    SYSTEM 


The  inferior  mesenteric  plexuses  is  situated  at  the  root  of  the  infe- 
rior mesenteric  artery  where  a  ganglion  is  found.  It  is  derived, 
chiefly,  from  the  left  side  of  the  aortic  plexus  and  gives  rise  to  sub- 
plexuses  that  follow  the  branches  of  the  artery,  as  the  left  colic  and 


Lefl  greater  splanchnic  r, 
Left  celiac  gang/ion 
Sup  mesenteric  artery 
left  renal  gonolion  • 
Sup  mesenteric ganglia 


Left, 


x/artery 


left  sympathetic  cord 


In?  mesenteric  ganctlic 


Left  Com.  //lac  artery 


Left  com  iliac  vein 
Hypogastric  plexus 


Fig.   329. — Abdominal  portion  of  the  sympathi  tic  trunk. 

sigmoid  plexuses  that  distribute  branches  to  the  corresponding  parts 
of  the  large  intestine  (descending,  iliac,  pelvic  colons  and  the  upper 
part  of  the  rectum). 

The  hypogastric  plexus  is  located  in  front  of  the  promontory  of  the 
sacrum  and  is  composed  of  branches  of  the  aortic  plexus  (the  hypo- 


THE   HYPOGASTRIC    PLEXUS  473 

gastric  nerves)  and  the  lumbar  ganglia.     Below  it  divides  into  right 
and  left  pelvic  plexuses  to  supply  the  pelvic  viscera. 

The  pelvic  plexuses  receive  branches  from  the  second,  third,  and 
fourth  sacral  nerves  and  a  few  from  the  first  two  sacral  sympathetic 
ganglia.  Small  ganglia  are  present.  Subplexuses  follow  the 
branches  of  the  internal  iliac  artery  (hypogastric).  The  subdivisions 
are  as  follows: 

1.  The  vesical  plexus  contains  a  large  number  of  spinal  nerve 
fibers  and  accompanies  the  branches  of  the  vesical  arteries.  Its 
branches  pass  to  the  bladder  and  ureter  and,  in  the  male,  to  the 
seminal  vesicles  and  vasa  deferentia  and  some  branches  join  the 
spermatic  plexus  on  the  spermatic  cord. 

2.  (a)  The  prostatic  plexus  is  large  and  sends  branches  to  the 
prostate,  neck  of  the  bladder,  seminal  vesicles  and  penis  of  the  male. 
In  the  latter  they  constitute  the  small  and  large  cavernous  nerves 
that  accompany  branches  of  the  internal  pudic  (pudendal)  artery. 

(b)  The  uterovaginal  plexus  sends  branches  to  the  uterus  along 
the  uterine  artery  and  these  join  those  of  the  ovarian  plexus.  The 
branches  to  the  vagina,  vestibule  and  clitoris  contain  quite  a  few 
spinal  nerve  fibers. 

3.  The  inferior  hemorrhoidal  plexus  sends  branches  to  the  lower 
part  of  the  rectum  and  these  join  the  branches  from  the  superior 
hemorrhoidal  plexus. 


INDEX 


Abdomen,  293 

apertures  of,  294 

boundaries  of,  293 

cavities  of,  293 

lines  of,  294 

lymphatics  of,  260 

muscles  of,  169 

regions  of,  294 

viscera  of,  293 
Abdominal  aorta,  235 
branches,  235 

rings,  1 70 
Abducens  nerve,  442 
Acetabulum,  93 
Acromion,  73 
Air  cells,  ethmoidal,  57 

sinuses,  frontal,  71 
mastoid,  352 
maxillary,  61 
sphenoidal,  57 
Ala  cinerea,  378 
Alimentary  tract,  282 
Alisphenoids,  49,  50 
Alveolar  process,  62 
Amphiarthroses,  10S 
Ampulla,  rectal,  307 

semicircular  canals,  353 

uterine  tube,  331 

vas,  326 
Amygdala,  41 1 
Anal  canal,  307 

columns,  307 

valves,  307 
Angle  of  mandible,  16 

of  scapula,  ;i, 

of  sternum,  35 

sacrovertebral,  35 

subcostal,  41 
Ankle  joint,  [38 
Annulus  ovalis,  218 
Anococcygeal  body,  177 
Ansa  hypoglossi,  433 
Antecubital  nodes,  25  7 
Anterior  rami  of  spinal  nerves,  451 
Antihelix,  350 
Antitragus,  35 


Antrum,  maxillary,  61 

pyloric,  301 

tympanic,  312 
Anus,  308 
Aorta,  225 

abdominal,  236 

arch  of,  225 

branches  of,  235 

great  sinus  of,  235 

thoracic,  235 

valves,  225 
Aortico-renal  plexus,  471 
Aperture  of  larynx,  275 

of  mouth,  282 

pyriform,  69 
Apertures  of  diaphragm,  168 

of  fourth  ventricle,  379,  414 

of  pelvis,  93 

of  thorax,  167 
Aponeurosis,  epicranial,  146 

intercostal,  166,  167 

palatal,  283 

palmar,  1X4 

plantar,  206 
Apparatus  digestorius,  282 

lacrimal,  34S 

respiratory,  271 

urinogenital,  316,  324 
Appendage,  pectoral,  73 

pelvic,  89 
Appendices  epiploica,  305 
Appendix  of  larynx,  276 

vermiform,  306 
Aqueduct  of  cerebrum,  3S1 
Aqueous  chamber,  346 

humor,  346 
Arachnoid,  362 

granulations,  362 

villi,  362 
Arbor  vita;  of  cerebellum,  408 
Arch,  alveolar,  <•: 

aortic,  223 

arterial  of  hand,  234 
of  wrist,  234 

carpal,  234 

dental,  69 


476 


Arch,  glossopalatal,  292 
neural,  24 

pharyngopalatal,  292 
plantar,  107 
Arcuate  fibers,  external,  409 

internal,  409 
Arteries,  ascending  pharyngeal,  228 
axillary,  231 
brachial.  232 
bronchial,  232 
of  brain,  431 
carotid,  common,  225 

external,  226 

internal,  229 
celiac,  236 
cerebral,  anterior,  430 

middle,  431 

posterior,  4.51 
cervical  ascending,  230 

deep,  231 

transverse,  229 
ciliary,  long,  347 

posterior,  347 

short,  347 
circumflex  of  humerus,  231,  232 

iliac,  239 

of  thigh,  239 
colic  left,  237 

middle,  236 

right,  236 
common  digital,  234,  240 
communicating  anterior,  430 

peroneal,  241 

tibial,  241 
coronary  of  heart,  225 

of  maxillary,  236 

of  stomach,  236 
costocervical  trunk,  231 
deferential,  23S. 
digital  of  foot,  241 

of  hand,  234 
dorsal  lingual,  236 

of  clitoris,  238 

of  penis,  238 
dorsalis  pedis,  240 

pollicis,  240 
epigastric  inferior,  238 

superficial,  239 

superior,  230 
esophageal,  235 
external  iliac,  238 
branches  of,  238 
maxillary,  226 
branches  of,  226 
facial,  226 


Arteries,  femoral,  238 

circumflex  deep,  239 
lateral,  239 
medial,  239 
fibular,  240 
frontal,  229 
gastric,  236 
gastroduodenale,  236 
gastroepiploic  left,  236 

right,  236 
gluteal,  237 
hemorrhoidal  inferior,  238 

middle,  238 

superior,  237 
hepatic,  236 

branches  of,  236 
hypogastric,  237 
ileocolic,  236 
iliac  common,  237 

external,  238 

internal,  237 
iliolumbar,  237 
infraorbital,  228 
innominate,  225 
intercostal,  233 
intestinal,  236 
labial,  226 
lingual,  226 
lumbar,  237 
malleolar,  241 
mammary,  230 
maxillary  external,  226 

internal,  228 
median,  233 
mediastinal,  235 
meningeal,  middle,  228 
mesenteric  inferior,  237 

superior,  236 
metacarpal,  233 
metatarsal,  240 
musculophrenic,  230 
nasal,  226 
obturator,  237 
occipital,  226 
of  eyeball,  347 
of  peni- 

ophthalmic,  229 
ovarian,  237 
palatal  ascending,  226 

descending,  229 
pancreatic,  236 
pancreaticoduodenale,  236 
perforating  of  foot,  241 

of  femoral,  239 

of  hand,  234 


477 


Arteries,  perforating,  of  peroneal,  241 
pericardial,  235 
peroneal,  241 
pharyngeal,  227 
phrenic,  23s 
plantar  lateral,  241 

medial,  241 
popliteal,  239 
posterior  auricular,  227 
pudendal,  238,  239 
pulmonary,  224 
radial,  232 
branches,  234 
indicis,  233 
renal,  237 
retinal,  229 
sacral,  237 
scapular,  230 
spermatic,  237 
spinal,  431 
subclavian,  229 
subcostal,  235 
sublingual,  226 
submaxillary,  226 
subscapular,  231 
superior  thyreoid,  226 
supraorbital,  229 
suprarenal,  23G 
temporal,  228 
thoracoacromial,  231 
thoracodorsal,  231 
thyrocervical  trunk,  229 
thyreoid  inferior,  229 

superior,  226 
tibial  anterior,  240 

posterior,  240 
tonsillar,  226 
ulnar,  233 
uterine,  238 
vaginal,  238 
vertebral,  229 
vesical  inferior,  238 
middle,  238 
superior,  238 
Arthrodia,  109 
\rti.  ular  discs,  in 

processes,  25 
Articulations,  108 

acromioclavicular,  126 
ankle,  138 

atlantoepistropheal,  113 
atlantooccipital,  114 
calcaneocuboid,  139 
carpal,  1 26 
carpometacarpal,  128 


Articulations,  costochondral,  11 
costotransverse,  117 
costovertebral,  116 
humeroradial,  123 
humeroulnar,  123 
interchondral,  119 
intermetacarpal,  128 
intermetatarsal,  141 
interphalangeal,  129,  142 
intertarsal,  139 
lumbosacral,  113 
mandibular,  115 
metacarpophalangeal,  128 
of  elbow,  1 23 
of  hip,  131 
of  knee,  134 
of  pelvis,  129 
of  pubis,  130 
of  shoulder,  127 
of  vertebrae,  in 
radiocarpal,  125 
radioulnar,  124 
sacrococcygeal,  113 
sacroiliac,  129 
sternoclavicular,  119 
sternocostal,  118 
tarsometatarsal,  140 
tibiofibular,  137 
tibiotarsal,  138 
Aryepiglottic  folds,  274 
Arytenoid  cartilages,  224 
Association  fibers  of  cerebrum,  416 
of  oblongata,  400 
of  spinal  cord,  367,  368,  369 
Atrioventricular  apertures,  217,  220 

bundle,  221 
Atrium  left,  219 

right,  217 
Attic,  tympanic,  351 
Auditory  area,  392 
canal,  350 
labyrinth,  353,  354 
meatus,  350 
nerve,  356 
ossicles,  352 
tube,  353 
Auricle,  217,  219,  350 
Axilla,  232 
Axis  cylinder,  359 

Bartholin,  glands  of,  335 
Basal  ganglia,  410 
Base  of  brain,  371 

of  heart,  216 

of  skull,  70 


4?S 


Basilar  groove,  377 

Bicipital  groove,  77 

Bile  ducts,  314 

Bladder,  319 

Blind  spot,  345 

Blood  vascular  system,  2IJ 

Bone  or  bones,  atlas,  26 

axi>.  2; 

calcaneus,  103 

cancellous,  19 

carpal,  S5 

clavicle,  73 

coccyx,  33 

compact,  19 

composition,  17 

conchal,  58 

development  of,  21 

diaphysis,  27 

ear,  352 

epiphysis,  27 

ethmoid,  56 

facial,  60 

flat,  23 

frontal,  41 

haversian  canals,  19 
systems,  19 

hip,  90 

humerus,  77 

ilium,  90 

incus.  352 

innominate,  90 

irregular,  23 

ischium.  92 

lacrimal,  58 

lacunae,  19 

lamellae,  19 

long,  23 

malleus,  352 

mandible,  65 

marrow.  :o 

maxilla,  60 

metacarpal.  87 

metatarsal,  103 

nasal,  59 

occipital.  4- 

of  foot,  107 

of  hand,  85 

palate,  63 

parietal,  43 

patella,  97 

pelvis,  89 

periosteum,  17 

phalanges,  87,  106 

pubis,  92 

radius,  82 


Bone  or  bones,  sacrum,  31 

scapula,  74 

sesamoid,  23 

short,  23 

sphenoid,  4S 

stapes,  352 

sternum,  35 

structure  of,  17 

tarsus,  103 

temporal,  52 

thigh,  94 

tibia,  9S 

ulna,  80 

vertebrae,  24 

Wormian,  23 

zygomatic,  64 
Brachia  conjunctiva,  379,  410 

of  midbrain,  379 

pontis,  377,  409 
Brain,  370 

base  of,  371 

circulation  of,  430 

fissures  of,  386 

hemispheres  of,  386 

lobes  of,  386 

parts  of,  371 

stem,  374,  393 

topography  of,  392 

ventricles  of,  413 

weight  of,  369 
Broad  ligament  of  uterus,  333 
Bronchi,  277 
Buccae,  2S4 
Bulb  of  corpus  spongiosum,  328 

of  urethra,  328 

of  vestibule,  335 

olfactory,  389,  426 
Bursae,  111 

Cai  Virus  scriptorius.  379 
Calyces  renales,  319 
Canal,  anal,  308 

hypoglossal,  47 

inguinal.  175 
Canine  fossa,  60 
Capsule,  external,  410 

internal,  411 

of  joints,  in 

of  Tenon,  341 
Cardia,  300 
Carotid  body,  340 
Cartilage.  109 
Caruncula  lacrimalis,  348 
Cauda  equina,  364 
Cavernous  plexus,  470 


479 


Cavernous  sinus,  432 

Cecum,  305 

Cells,  ethmoidal.  57 

mastoid,  352 
Cerebellum,  3S1,  40S 
Cerebrospinal  nerve  system,  360 
Cerebrum,  386,  410 
Cerumen,  350 
Ceruminous  glands,  350 
Chambers  of  eyeball,  346 
Cheeks,  284 
Chest,  40 
Choame,  274 
Chordae  tendineae,  219 
Choroid,  344 

plexus,  385 
Chromaphyl  system,  339 
Ciliary  body,  344 

ganglion,  444 

processes,  344 

ring,  344 
Cingulum,  388 
Circular  sinus  of  brain,  430 

of  eyeball,  347 
Circulation,  portal,  251 

pulmonary,  224 

systemic,  250 
Circumanal  glands,  30S 
Cisterna  eerebellomedullaris,  362 

chiasmatis,  362 

chyli,  253 

interpeduncularis,  362 

magna,  362 

subarachnoideales,  362 
Claustrum,  410 
Clava,  37  1 

Clinoid  processes,  48 
Clitoris,  336 
Coccygeal  ganglion,  470 

gland,  340 
Cochlea,  354 
Cochlear  duct,  355 
Colliculi,  380 
( lolon,  306 

ascending,  306 

descending,  306 

lie'. II res  of,  306 

pelvic.  306 

sigmoid,  307 

transverse,  306 
Columnae  1  arneae,  210 
Columns  of  Bertin,  317 

of  rectum.  307 

of  spinal  cord,    ;  16 
Comma  tract,  309 


Commissure,  anterior,  410,  42S 

gray,  364 

hippocampal,  416 

of  Gudden,  448 

posterior,  33s 

white,  366 
Cones,  retinal,  345 
Confluens  sinuum,  461,  432 
Conjunctiva,  348 
Conus  arteriosus,  218 

medullaris,  362 
Coracoid  process,  76 
Cord,  ganglionated,  466 
Cords  of  brachial  plexus,  453 
Cornea,  343 
Cornicula  laryngis,  275 
Corona  dentis,  286 

glandis,  329 

radiata,  415 
Coronal  suture,  70 
Coronoid  fossa,  79 

process,  66,  80 
Corpora  albicantia,  383,  428 

quadrigemina,  380 
Corpus  adiposum  buccae,  284 

callosum,  390,  416 

cavernosum,  328 

geniculatum,  379,  384 

spongiosum,  328 

striatum,  411 
Cortex,  cerebral,  410 
Corti,  organ  of,  356 

spiral  ganglion  of,  354 
Cortical  localization,  391 
Corticifugal  projection  libers,  415 
Costal  cartilages,  39 
Cowper's  glands,  328 
Cranial  fossa-,  71 
Craniocerebral  topography,  392 
Cricoid  cartilage,  274 
Crura  ci  rebri,  379,  405 
Crusta,  403 
Crystalline  lens,  346 
Cuneale  fasciculus,  319 

nucleu 
Cuneiform  cartilages,  275 
Cuneus,  388,  392 
Cupola  of  cochlea,  354 

Dartos  fascia.  325 

Decussation,  brachia  conjunctiva,  4o£ 

fountain,  407 

lemnisci,  397 

motor,  375,  39s 

optic,  284 


480 


Decussation,  sensor,  397 

Deiter's  nucleus,  440 

Dendrites,  359 

Dens,  27 

Dental  arches,  287 

Dentate  gyre,  427 

nucleus,  408 
Diaphragm  sella;,  361 

urinogenitale,  176 
Diarthroses,  109 
Digastric  fossa,  66 
Digestive  system,  282 
Dorsum  sellae,  4S 
Ductless  glands,  338 
Ductus  endolymphaticus,  355 
Duodenum,  302 
Dura  mater,  361 

Ear,  external,  350 

internal,  353 

middle,  350 
Ejaculatory  duct,  327 
Enarthrodial  joints,  109 
Encephalon,  370 
Endolymph,  354 
Ependyma,  415 
Epididymis,  325 
Epigastrium,  295 
Epiglottic  cartilage,  274 
Epiglottis,  274 
Epiphyseal  line,  21 
Epiphysis,  27,  385 
Epithalamus,  386 
Epitympanic  recess,  352 
Eruption  of  teeth,  2S5 
Esophagus,  293 
External  auditory  canal,  350 
meatus,  350 

genitalia,  334 
Eyeball,  341 
Eyelids,  347 

Face,  71 
Facial  bones,  60 
Falx  cerebelli,  361 

cerebri,  361 
Fasciculus,  or  fasciculi,  anterior  pro- 
prius,  367 

anterolateral  superficial,  367 

cerebropontile,  401 

cerebrospinal,  366,  36S 

cervicolumbalis,  369 

cuneatus,  369 

gracilis,  368 

interfascicularis,  369 

lateralis  proprius,  368 


Fasciculus,  or  fasciculi,  longitudinalis 
medialis,  400,  40S 

olivospinal,  367 

posterior  proprius,  369 

posterolateralis,  369 

pyramidal,  416 

retroflexus,  3S6 

rubrospinal,  36S 

septomarginal,  369 

solitarius,  400 

spinocerebellar,  367,  368 

spinotectal,  36S 

spinothalamic,  367,  368 

striatothalamic,  412 

tectospinal,  366,  368,  400 

vestibulospinal,  367 
Fauces,  292 

Female  reproductive  organs,  330 
Femoral  canal,  195 

ring,  195 
Fenestra  cochlea;,  351 

vestibularis,  351 
Fibers,  arcuate,  external,  39S,  409 
internal,  409,  410 

association,  416 

commissural,  4r6 

corticostriate,  413 

corticothalamic,  413 

projection,  415 

thalamocortical,  4r2 
Fibrocartilage,  109 
Filiform  papillae,  28S 
Filtration  angle,  346 
Filum  terminale,  363 
Fimbria  of  uterine  tube,  331 
Fissure  or  fissures,  calcarine,  388 

central,  386 

cingular,  3SS 

circular,  386 

collateral,  388 

frontal,  3S8  » 

hippocampal,  3S8 

lateral,  3S6 

longitudinal,  386 

occipital,  3SS 

of  cerebellum,  3S3 

of  cerebrum,  386 

of  liver,  311 

of  lung,  280 

of  oblongata,  375 

of  spinal  cord,  364 

orbital,  51,  6S,  388 

palpebral,  347 

parietal,  388 

portal,  311 


48 1 


Fissure  or  fissures,  sphenoidal,  5  i .  68 

sylvian,  386 

temporal,  388 
Flexures,  cervical,  35 

lumbar,  35 

of  colon,  300 

of  rectum,  307 

of  sacrum,  35 

of  vertebral  column,  34 

thoracic,  35 
Folds,  peritoneal,  296 
Fontanelles,  70 
Foot,  arteries  of,  139 

bones  of,  103 

muscles  of,  207 
Foramen  or  foramina,  alveolaria,  61 

cecum,  43,  287 

condyloid,  70 

epiploic,  296 

incisive,  62 

infraorbital,  61 

interventricular,  413 

intervertebral,  34 

jugular,  71 

lacerum,  70,  71 

magnum,  48,  70 

mastoid,  70 

mental,  65 

obturator,  93 

of  Luschka,  414 

of  Magendie,  379,  414 

optic,  68 

ovale,  70 

rotundum,  71 

spinosum,  70 

stylomastoid,  70 

supraorbital,  42 

vena  cava?,  168 

vertebral,  25 

Winslowi,  296 
Formatio  reticularis,  398 
Fornix,  390,  429 
Fossa,  or  fossx,  anterior,  71 

canine,  60 

condyloid,  47 

coronoid,  80 

cranial,  71 

digastric,  66 

digital,  323 

for  gall-bladder,  311 

glenoid,  76 

iliac,  96 

incisor,  6o,  63 

infraspinous,  74 

infratemporal,  69,  70 
3i 


Fossa    or  fossa?,  interpeduncular,  379 

ischiorectal,  174 

jugular,  55 

lacrimal,  43,  68 

middle,  71 

nasal,  99,  271 

orbital,  38,  341 

ovarian,  330 

popliteal,  239 

pterygoid,  51,  70 

pterygopalatine.  51,  70 

radial,  80 

scaphoid,  70 

submaxillary,  66 

supraspinous,  74 

supratonsillar,  292 

temporal,  69 

trochanteric,  94 
Fourchette,  335 
Fourth  ventricle,  378,  414 
Fovea  centralis,  345 
Frenulum  linguae,  288 

labii,  284 

preputii,  329 
Frontal  tuberosity,  42 
Fundus  of  stomach,  301 

of  uterus,  332 
Fungiform  papillae,  288 

Galea  aponeurotica,  r46 

Gall  ducts,  314 

Gall-bladder,  313 

Ganglion  or  ganglia,  aorticorenal,  471 

basal,  410 

cardiac,  470 

celiac,  470 

cervical,  467 

ciliary,  444 

coccygeal,  470 

cochlear,  438 

Gasserian,  443 

geniculate,  441 

habenulx',  386,  429 

interpedunculare  386 

jugular,  438 

lumbar,  469 

nodosum,  438 

of  Corti,  438 

otic,  446 

petrous,  438 

sacral,  469 

semilunar,  443 

sphenopalatine,  445 

spinal,  449 

submaxillary,  446 


48  2  in 

Ganglion  or  ganglia, sympathetic,  466, 
467  _ 

thoracic,  469 

vestibular,  438 
Ganglionated  cord,  400 
Geniculate  bodies,  379,  384 

ganglion,  441 
Genu  of  corpus  callosum,  390 

of  facial  nerve,  441 

of  internal  capsule,  412 
Giacomini,  427,  428 
Gingiva;,  284 
Ginglymus,  109 
Girdle,  pectoral,  73 

pelvic,  89 
Glabella,  42 
Glans  clitoris,  336 

penis,  329 
Globus  pallidus,  44 
Glomus  caroticum,  340 
Glossopalatal  arch,  292 
Glottis,  276 
Goll,  tract  of,  36S 
Gowers'  tract,  367 
Gracilis,  funiculus,  368 

nucleus,  397 
Gums,  2S4 
Gustatory,  392 

Habenula,  ganglion  of,  386 
Hair  cells,  auditory,  356 
Hard  palate,  284 
Haversian  canals,  19 

systems,  19 
Heart,  215 

outline  of,  222 
Helicotrcma,  354 
Helix,  350 
Hemispheres,  cerebellar,  381 

cerebral,  386 
Hilus  of  kidney,  317 

of  lungs,  278 

of  nucleus  dentatus,  408 
olivarius,  400 

of  spleen,  269 

suprarenal  gland,  339 
Hip  joint,  131 
Hippocampal  fissure,  3S8 
Hippocampus,  391,  427,  429 
Humor,  aqueous,  346 

vitreous,  346 
Hyalin  cartilage,  109 
Hymen,  335 
IIvpoi  hondrium,  295 
Hypogastrium,  295 


Hypophysis,  383 
Hypothalamus,  3S4 

Ileocecal  valve,  305 
Ileopectineal  eminence,  92 

line,  92 
Ileum,  304 
Iliac  crest,  90 

spines,  90 
Impression,  cardiac,  309 

colic,  310 

gastric,  269 

hepatic,  269 

renal,  310 

splenic,  269 
Incisura  angularis,  301 

cardiaca,  278 
Indusium,  427 
Inframammary  region,  213 
Inguinal  canal,  173 

ligament,  170 

ring,  170 
Insula,  388 

Intercondylic  fossa,  96 
Intercostal  aponeuroses,  166,  167 
Internal  capsule,  411 
Interosseous  membrane,  124,  137 
Interpleural  space,  213 
Interscapular  region,  313 
Intertubercular  plane,  294 
Interventricular  foramen,  413 

grooves,  217 
Intervertebral  cartilages,  in 
Intestine,  large,  305 

small,  302 
Intumescentia  cervicalis,  362 

lumbalis,  362 
Ins.  345 

Island  of  Reil,  3S8 
Isthmus  of  fauces,  292 

of  pharynx,  292 

of  uterine  tube,  331 
Iter,  3S1 

Jaw,  mandible,  65 

maxilla,  60 
Jejunum,  305 
Joints,  108 
Jugular  foramen,  7c 

process,  47 

Kidneys,  316 
Kronlein's  methods,  392 

Labia  majora,  335 
minora,  335 


Labia  oris,  2S2 
Labrum  glenoidale,  122 
Labyrinth  ethmoidal,  57 
membranous,  354 
osseous,  353 
Lacrimal  apparatus,  348 
duct,  340 
fossa,  42,  68 
gland,  ,us 
Lamina  terminalis,  384 
Larynx,  272 

interior  of,  274 
Lateral  or  transverse  sinus,  432 
of  fourth  ventricle,  414 
of  pharynx,  292 
ventricles,  391,  413 
Lemniscus,  lateral,  403 

medial,  307,  308,  406,  4rg 
Lens,  crystalline,  346,  423 
Lenticular  nucleus,  411 
Ligaments,  109 

peritoneal  folds,  296 
Line  or  lines,  aspera,  95 
intertubercular,  294 
lateral  sternal,  211 
midaxillary,  211 
midclavicular,  211 
midsternal,  211 
midvertebral,  211 
mylohyoid,  66 
of  abdomen,  294 
of  thorax,  211 
parasternal,  21  r 
Poupart,  294 
scapular,  211 
subcostal,  294 
transpyloric,  294 
Lips,  283 

Lobe  or  lobes,  caudate,  311 
central,  388 
cerebellar,  3S1,  382 
cerebral,  388 
frontal,  388 
oi  cipital,  3S8 
of  liver,  311 
of  lungs,  279 
olfactory,  38S 
parietal,  388 
temporal,  388 
Locus  cceruleus,  378 
Lumbar  plexus,  458 

regions,  295 
Lungs,  277 

outline  of,  281 
Lymph,  253 


Lymph  nodes,  253 
aortic,  261 

axillary,  257 

cervii  al,  256 

fai  ial,  255 

gastric,  263 

hypogastric,  261 

inguinal,  259 

lingual,  250 

lumbar,  261 

mesenteric,  262,  264 

occipital,  234 

of  abdomen,  260 

of  head  and  neck,  254 

of  liver,  264 

of  lower  extremity,  259 

of  neck,  256 

of  thorax,  265 

of  upper  extremity,  257 

parotid,  254 

popliteal,  259 

subclavian,  259 

submaxillary,  256 

suprapancreatic,  262 

tracheobronchial,  267 
trunks,  254 
vascular  system,  252 

Macula  acustica,  355 

lutea,  343 
Malleolus,  100,  102 
Mammary  gland,  366 
Mammillary  bodies,  383,  428 
Marrow,  20 
Marshall,  fold  of,  221 
Mastoid  cells,  352 
Maxillary  sinus,  61 
Meatus,  acoustic,  350 

of  nose,  inferior,  271 
middle,  271 
superior,  271 
Median  longitudinal  bundle,  400, 
Mediastinum,  213 
Membrana  tympani,  352 
Membranes  of  brain,  361 

of  Reissner,  356 
Membranous  labyrinth,  354 
Meninges,  .i'11 
Mesem  ephalon,  378 
Mesentery,  296 
Metathalamus,  384 
Midbrain.  378 
Middle  ear,  351 

Mitral  valve,  220 
Moderator  band,  218 


484 


Modiolus,  354 
Mons  veneris.  335 
Motor  area,  3gi 

decussation,  305 

pathway,  direct,  416 
indirect,  418 
Mouth,  282 
Muscles,  140 

movements  of,  145 

of  abdomen,  169 

of  arm,  181 

of  back,  160 

of  buttock,  iog 

of  cervical  region,  153,  159 

of  ear,  146,  352 

of  eyeball,  341,  149 

of  foot,  207 

of  forearm  and  hand,  1S3 
dorsal,  190 
ventral,  184 

of  infrahyoid  region,  154 

of  larynx,  276 

of  leg,  dorsal,  205 
lateral,  205 
ventral,  203 

of  little  finger,  189 

of  mastication,  I5r 

of  nasal  region,  148 
of  neck,  153,  159 

of  oral  region,  148 

of  orbital  region,  149,  341 

of  pectoral  region,  177 

of  pelvis,  174 

of  perineum,  1  74 

of  pharynx  and  palate,  157 

of  scalp,  146 

of  shoulder  region,  179 

of  suprahyoid  region,  165 

of  thigh,  dorsal,  201 
medial,  197 
ventral,  195    • 

of  thorax,  166 

of  thumb,  188 

of  tongue,  156,  288 

structure  of,  143 

tissue,  143 
Myocardium,  220 
Myology,  143 

Nasal  aperture,  271 

cavity,  271 

fossa,  271 
Nasal  cavity,  271 
Nasolacrimal  duct,  349 
Nerve  or  nerves,  abducens,  442 


Nerve  or  nerves,  accessory,  435 
acustic,  439 
alveolar,  445,  446 
anococcygeal,  465 
ansa  hypoglossi,  453 
auricular,  452 
auriculotemporal,  446 
axillary,  456 
cardiac,  468,  438 
cerebral,  433 
cervical,  450 
chorda  tympani,  441 
circumflex,  456 
coccygeal,  45  r 
cochlear,  439 
common  peroneal,  464 
deep  peroneal,  465 
descendens  hypoglossi,  453 
digital  of  foot,  463 

of  hand,  435 
encephalic,  433 
facial,  441 
femoral,  461 
frontal,  444 
genitofemoral,  466 
glossopharyngeal,  436 
gluteal,  465 
hypoglossal,  434 
iliohypogastric,  459 
ilioinguinal,  459 
inferior  maxillary,  445 
infraorbital,  445 
intercostobrachial,  453 
intermedius,  441 
laryngeal,  internal,  438 

external,  438 

recurrent,  438 

superior,  438 
lingual,  446 
lumbar,  451 
mandibular,  445 
masticatory,  446 
maxillary,  445 
mental,  446 
musculocutaneous,  434 
musculospiral,  456 
nasociliary,  444 
nasopalatine,  445 
obturator,  460 
occipital,  450 
oculomotor,  447 
olfactory,  449 
ophthalmic,'  444 
optic,  447 
palatine,  445 


Nerve  or  nerves,  perineal,  465,  466 
peroneal  common,  41. 4 

deep,  465 

superficial,  465 
petrosal,  441 
pharyngeal,  438 
phrenic,  453 
plantar,  463 
popliteal  external,  464 

internal,  463 
pudendal,  465 
pulmonary,  470 
radial,  456 
sacral,  451 
saphenous,  451 
scapular,  454 
sciatic,  461 
spinal,  449 

dorsal  rami  of,  450 

ganglion  of,  440 

ventral  rami  of,  451 
splanchnic,  469 
superficial  peroneal,  465 
superior  maxillary,  445 
supraorbital,  444 
sural,  464 
sympathetic,  466 
thoracic,  450 
thoracodorsal,  437 
tibial,  463,  465 

recurrent,  464 
trigeminal,  443 
trochlear,  446 
ulnar,  456 
vagal,  436 
vestibular,  439 
zygomatic,  445 
zygomaticofacial,  445 
zygomaticotemporal,  445 
Nerve  cells,  35S 
fibers,  359 
system,  358 

peripheral,  433 
Neurilemma,  359 
Neuroglia,  359 
Neuron,  358 
Nipple,  337 

Nucleus  or  nuclei,  ambiguus,  400 
amygdala-,  411 
caudate,  411 
cochlear,  439 
cuneus,  397 
dentate,  408 
dorsalis,  465 
emboliform,  408 


Nucleus  or  nuclei,  fastigii,  408 

globosus,  408 

gracilis,  397 

hypoglossal,  434 

insertus,  402 

intercallatus,  402 

laryngeal  (nidus),  433 

lateral  of  thalamus,  431 

lenticular,  411 

medial  of  thalamus,  413 

of  abducens  nerve,  402 

of  accessory  nerve,  440 

of  Bechterevv,  440 

of  Clarke,  365 

of  Deiter,  440 

of  facial  nerve,  403,  439 

of  funiculus  solitarius,  400 

of  glossopharyngeal  nerve,  436 

of  lateral  lemniscus,  405 

of  median  longitudinal  bundle,  408 

of  mesencephalon,  408 

of  oculomotor  nerve,  406,  447 

of  tegmentum,  406 

of  thalamus,  413 

of  tractus  solitarius,  400 

of  trapezoid  body,  403 

of  trigeminal  nerve,  443 

olivary,  400 

pontis,  400 

red,  406 

thoracalis,  365 

trochlear,  406,  446 

vagal,  436,  437 

vestibular,  402,  439 
Nymphse,  335 

Oblongata,  374,  395 
Olecranon,  80 
Olfactory  area,  392 

bulb,  389,  426 

lobe,  389 

mucosa,  271 

stria.',  426,  429 

tract,  389,  426 
Olivary  nucleus,  400 
Olive,  375,  400 
Omental  bursa,  297 

tuberosity,  310 
Omentum,  296 
Opercula  insula?,  388 
Optic  axis,  343 

chiasm,  383,  448 

commissure,  44S 

foramen,  68 

nerve,  340,  448 


486 


Optic  radiation,  448 

thalami,  385 

tract.  448 
Ora  serrata,  345 
Oral  cavity,  284 
Orbit,  68,  341 
Organ  of  Corti,  356 
Ossicles,  auditory,  352 
Ossification  of  bone,  21 
Otic  ganglion,  446 
Ovary,  330 
Oviduct,  331 

Palatal  aponeurosis,  285 
Palate,  284 
Palpebral,  347 
Pampiniform  plexus,  325 
Pancreas,  314 
Papillae,  lingual,  287 
Parametrium,  3^3 
Parasympathetics,  340 
Paratliyreoid  bodies,  338 
Parotid  gland,  289 
Pathway,  auditory,  423 
gustatory,  421 

motor,  direct,  416 
indirect,  418 

muscle  sense,  424 

olfactory,  426 

optic,  420 

reflex,  419 

respiration,  425 

sensor,  419 

touch  and  pressure,  424 
Peduncles  of  cerebellum,  383,  408 

of  cerebrum,  370,  405 
Pelvic  cavity,  294 
Pelvis,  93 
Penis,  328 

Perforated  substance,  427 
Pericardium,  221 
Perichondrium,  109 
Perilymph,  354 
Perimysium,  143 
Perineurium,  360 
Periosteum,  18 
Peritoneal  cavity,  296 
Peritoneum,  296 
Perivascular  lymph  spaces,  252 
Permanent  teeth,  285 
Pharynx,  290 
Philtrum,  283 
Pia,  362 

Pillars  of  fornix,  390 
Pineal  body,  3S5 


Plantar  arch,  241 
Pleura1,  279 
Pleural  cavity,  279 

outline,  279 
Plexus  or  plexuses,  aortic,  471 

brachial,  453 

cardiac,  470 

carotid,  470 

cavernous,  470 

celiac,  470 

cervical,  451 

choroidal,  385 

coronary,  471 

esophageal,  470 

hemorrhoidal,  473 

hepatic,  471 

hypogastric,  472 

lumbar,  458 

mesenteric,  471 

ovarian.  471 

pampiniform,  325 

pelvic,  473 

pharyngeal,  438 

phrenic,  471,  472 

prostatic,  473 

pudendal,  465 

pulmonary,  470 

renal,  471 

sacral,  470 

sigmoid,  472 

splenic,  471 

suprarenal,  471 

uterine,  473 

vaginal,  473 

vesical,  473 
Plica  or  plicae,  circulares,  302 

fimbriata,  288 

glossocpiglottic,  2S8 

palmate,  322 

salpingopalatal,  292 

salpingopharyngeal,  292 

sublingual,  2S5 

umbilical,  322 

ureteric,  322 

ventricularis,  275 

vocalis,  275 
Pons  (varolii),  377,  400 
Portal  circulation,  25 j 
Posterior  chamber,  346 

commissure,  335 
Prepuce,  329 
Pudendum,  334 
Pulmonary  circulation,  224 
Pulvinar,  384 
Puncta  lacrimalia,  348 


487 


Puncta  maxima,  222 
Pupil,  345 
Putamen,  41 1 
Pyloric  antrum.  301 
I\  lorus,  300 
Pyramidal  colls,  416 
Pyramids,  375,  395,  401 
Pyriform  aperture,  60 

QUADRIGEMINAL  bodies,  380,  405 

Radiation,  auditory,  412 

of  corpus  striatum,  412 

optic.  448 
Rami  communicantes,  gray,  466 

white,  467 
Raphe  of  oblongata,  398 

of  palate.  284 

of  pons,  402 

of  scrotum,  384 
Recess,  epitympanic,  351 

lateral  of  fourth  ventricle,  414 

of  infundibulum,  413 

of  pharynx,  292 

optic.  413 

pineal,  413 
Rectal  ampulla,  307 

valves,  307 
Rectum,  307 
Red  marrow,  20 

Refracting  media  of  the  eyeball,  346 
Regions  of  abdomen,  294 

of  thorax,  21  2 
Respiratory  system,  271 
Restiform  body,  377,  408 
Retina,  345 
Ring,  inguinal,  170 

Saccule,  354 
Sclera,  344 
Scrotum,  324 
Sella  turcica,  48 
Semicircular  canais,  bony,  353 

membranous,  355 
Semilunar  ganglion,  443 
Seminal  vesicles,  326 
Sensor  area  of  brain,  391 

decussation,  397 

pathway,  419 
Septomarginal  tract,  369 
Septum  lucidum,  391,  428 
Sigmoid  colon,  307 

mesocolon,  307 
Sinus  cavernosus,  432 

circular,  432 


Sinus  coronary,  218 

frontal,  71 

great  oblique,  221 
transverse,  221 

intercavernous,  432 

lateral,  432 

longitudinal,  432 

maxillary,  61 

of  cranium,  432 

of  dura,  432 

petrosal,  inferior,  432 
superior,  432 

phrenicocostal,  270 

rectal,  308 

sagittal,  inferior,  432 
superior,  432 

sphenoidal,  71 

sphenoparietal,  432 

squamopetrosal,  432 

straight,  432 

transverse,  432 
Skeleton,  appendicular,  17 

axial,  17 
Skull,  41 

as  a  whole,  67 
Sounds  of  the  heart,  222 
Space,  axillary,  232 

interpleural,  213 

mediastinal,  213 

subarachnoid,  362 

subdural,  362 
Spaces,  lymph,  232 

of  Fontana,  347 
Spermatic  cord,  325 
Spinal  canal,  415 

cord,  362 

ganglia,  449 

nerves,  449 
Splanchnic  nerves,  469 
Spleen,  268 

Splenium  of  corpus  callosum,  416 
Spongy  bone,  19 
Sternal  angle,  35 
Stomach,  300 

bed,  300 

chamber,  300 
Stria?  mcdulares,  378,  423 
Subarachnoid  space,  362 
Subcostal  angle,  41 
Subdural  space,  362 
Sublingual  gland,  290 
Submaxillary  ganglion,  446 

gland,  ?qo 
Substantia  ferruginea,  378 

gelatinosa,  366,  397 


Substantia  nigra,  405 

Sulci.     See  Fissures. 

Suprarenal  gland,  339 

Supratonsillar  fossa,  292 

Sutures,  108 

Sympathetic  nerve  system,  466 

Symphysis  of  mandible,  65 

pubis,  93 
Synarthrosis,  108 
Synchondrosis,  108 
Syndesmology,  10S 
Synovial  bursae,  1 1 1 

membrane,  1 1 1 
Systemic  circulation,  250 

Tarsus,  103 
Taste  buds,  287 
Teeth,  285 

Tegmentum  of  pons,  377,  406 
Tela  choroidea,  400 
Temporal  fossa,  69 
Temporopontile  tract,  412 
Tentorium  cerebelli,  361 
Testes,  324 

Thalamocortical  fibers.  412 
Thalamostriate  fibers,  412 
Thalamus,  385,  412 
Thebesius,  foramina  of,  218 
Third  ventricle,  413 
Thoracic  duct,  252 
Thorax.  42 

boundaries  of,  42 

lines  of.  211 
Thymus  gland,  270 
Thyreoid  cartilage,  273 

gland,  338 
Tongue,  287 
Tonsil,  lingual,  288 

palatal,  292 

pharyngeal,  292 
Trachea,  276 
Tract.     See  Fasciculus. 

olfactory,  389,  426 

optic,  418 
Tragus,  350 
Transpyloric  line,  295 
Trapezium,  403 
Trigonum  habenuhe,  386 

hypoglossi,  378 

olfactory,  426 

vagi,  378 

vesicae,  322 
Trochanter,  94 

Trunks  of  brachial  plexus,  453 
Tube,  auditory,  353 


Tube,  uterine,  331 
Tuber  cinereum.  383 

omentale,  310 
Tunnel  of  Corti,  356 
Tympanic  antrum,  352 

atrium,  351 

attic,  351 

cavity,  351 

membrane,  352 

ossicles,  352 
Tympanum,  352 

Umbo  membranae,  352 
Uncus,  427 
Urachus,  322 
Ureter,  319 
Urethra,  crest  of,  323 

female,  323 

male,  323 
Urinary  bladder,  319 
Uterine  tube,  331 
Uterus,  332 
Utricle,  354 
Uvula  cerebelli,  383 

palatina,  285 

vesicae,  322 

Vagina,  334 
Vallate  papillce,  288 
Vallecula,  228 
Valves  aortic,  229 

bicuspid,  220 

colic,  305 

pulmonary,  224 

pyloric,  302 

rectal,  307 

sinus  coronarii,  218 

tricuspid,  217 
Valvula,  404 
Vas  deferens,  326 
Vascular  system,  211 
Vein,  or  veins,  azygos,  249 

cardiac,  221 

cava,  inferior,  247 
superior,  245 

internal  jugular,  242 

of  abdomen,  247 

of  brain,  431 

of  extremities,  lower,  245 
upper,  24.5 

of  head,  243 

of  spinal  cord,  432 

portal,  251 

pulmonary,  '248 
Velum  interpositum,  385 


489 


Ventrii  les,  cerebral,  413 

fourth,  378,  413 

lateral,  391,  413 

of  heart,  218,  220 

of  larynx,  275 

third,  3S6,  413 
Vertebra,  24 

cervical,  25 

coccygeal,  33 

lumbar,  29 

prominens,  28 

sacral,  31 

thoracic,  28 

Vertebral  column,  24 

as  a  whole.  34 

curves  of,  34 

Vestibular  ganglion,  j  (8 

Vestibule,  aortic,  220 

bulb  of,  335 


Vestibule,  of  labyrinth,  353 

of  larynx,  275 

of  mouth,  283 

of  nose,  271 

of  vagina,  335 
Vibrissas,  271 
Villi  arachnoideale,  362 

of  intestine,  304 
Visual  area,  392 

axis,  343 
Vitreous  body,  346 
Vocal  cords,  275 
Vulva,  334 

Willis,  circle  of,  430 

Womb,  332 
Wrist,  85 

Xyphoid  process,  36 


SAUNDERS'  BOOKS 


Skin,  Genito- Urinary, 

Chemistry,  Eye,  Ear,  Nose, 

and  Throat,  and  Dental 

W.  B.  SAUNDERS   COMPANY 

WEST  WASHINGTON  SQUARE  PHILADELPHIA 

9,  HENRIETTA   STREET,   COVENT  GARDEN,  LONDON 

Davis'    Accessory  Sinuses 

Development  and  Anatomy  of  the  Nasal  Accessory  Sinuses  in 
Man.  By  Warren  B.  Davis,  M.  D.,  Corinna  Borden  Keen  Research 
Fellow  of  the  Jefferson  Medical  College,  Philadelphia.  Octavo  of  172 
pages,  with  57  original  illustrations.  Cloth,  $3.50  net. 

ORIGINAL  DISSECTIONS 

This  book  is  based  on  the  study  of  two  hundred  and  ninety  lateral  nasal  walls, 
presenting  the  anatomy  and  physiolog)  of  the  nasal  accessory  sinuses  from  the 
sixtieth  day  of  fetal  life  to  advanced  maturity.  It  represents  the  original  research 
■work  and  personal  dissections  of  Dr.  Davis  at  the  Daniel  Baugh  Institute  of 
Anatomy  of  Philadelphia  and  at  the  Friedrichshain  Krankenhaus  of  Berlin.  It 
was  necessary  for  Dr,  Davis  to  develop  a  ;.v:<.'  technic  by  which  the  accessory 
sinus  areas  could  be  removed  en  masse  at  the  time  of  postmortem  examinations, 
and  still  permit  of  reconstruction  of  the  face  without  marked  disfigurement. 
Ninety-six  cases  in  this  series  were  thus  obtained.  The  tables  of  averages,  giving 
you  the  age,  size  of  ostia,  origin,  thickness  of  septum,  and  anterior  and  posterior 
walls,  vertical,  lateral,  and  posterior  diameters,  and  relation  to  the  nasal  floor, 
form  an  extremely  valuable  feature. 


SAUNDERS'    BOOKS    ON 


StelwagonV 
Diseases  of  the  Skin 


A  Treatise  on  Diseases  of  the  Skin.  By  Henry  W.  Stelwagon, 
M.  D.,  Ph.  D.,  Professor  of  Dermatology  in  the  Jefferson  Medical 
College,  Philadelphia.  Octavo  of  1309  pages,  with  356  text-cuts  and 
12,  plates.  Cloth,  $6.50  net;   Half  Morocco,  #8.00  net. 

NEW  (8th)  EDITION 

There  are  two  features  in  Dr.  Stelwagon's  work  that  stand  out  above  all  the 
others  :  The  special  emphasis  given  the  two  practical  phases  of  the  subject — 
diagnosis  and  treatment ;  and  the  -wealth  of  illustrations.  These  latter  are  of  real 
value.  They  teach  you  diagnosis  as  no  description  can.  Many  of  these  illustra- 
tions are  in  colors. 

Over  75  pages  of  the  work  are  devoted  to  syphilis,  giving  you  the  Wassermann 
test,  the  salvarsan  ("606")  treatment,  and  all  the  newest  advances.  Pellagra, 
tropical  affections,  hookworm  disease,  Oriental  sore,  ringworm,  impetigo  contagiosa 
— all  those  diseases  being  so  widely  discussed  to-day. 

George  T.  Elliot,  M.  D„   Professor  of  Dermatology,  Cornell  University. 

"  It  is  a  book  that  I  recommend  to  my  class  at  Cornell,  because  for  conservative  judgment, 
for  accurate  observation,  and  for  a  thorough  appreciation  of  the  essential  position  of  derma- 
tology, I  think  it  holds  first  place." 


Schamberg's  Diseases  of  the  Skin 
and  Eruptive  Fevers 


Diseases  of  the  Skin  and  the  Eruptive  Fevers.  By  Jay  F.  Schamberg, 
M.  D.,  Professor  of  Dermatology  and  the  Infectious  Eruptive  Diseases,  Philadel- 
phia Polyclinic.      Octavo  of  5S5  pages,  illustrated.      Cloth,  S3. 25  net. 

NEW  (3d)  EDITION 

"  The  acute  eruptive  fevers  constitute  a  valuable  contribution,  the  statements  made 
emanating  from  one  who  has  studied  these  diseases  in  a  practical  and  thorough  manner  from 
the  standpoint  of  cutaneous  medicine.  .  .  .  The  views  expressed  on  all  topics  are  con- 
servative, safe  to  follow,  and  practical,  and  are  well  abreast  of  the  knowledge  of  the  present 
time,  both  as  to  general  and  special  pathology,  etiology,  and  treatment."— American  Journal 
*f  Medical  Sciences. 


GEA'I  TO- URINARY  DISEASES 


Norris' 
Gonorrhea  in  Women 

Gonorrhea  in  Women.  By  Charles  C.  Norris,  M.  D.,  Instructor 
in  Gynecology,  University  of  Pennsylvania,  with  an  Introduction  by 
John  G.  Clark,  M.  D.,  Professor  of  Gynecology,  University  of  Penn- 
sylvania.    Large  octavo  of  520  pages,  illustrated.  Cloth,  $6.50  net 

A  CLASSIC 

Dr.  Norris  here  presents  a  work  that  is  destined  to  take  high  place  among 
publications  on  this  subject.  He  has  done  his  work  thoroughly.  He  has  searched 
the  important  literature  very  carefully,  over  2300  references  being  utilized. 
This,  coupled  with  Dr.  Norris'  long  experience,  gives  his  work  the  stamp  of 
authority.  The  chapter  on  serum  and  vaccine  therapy  and  organotherapy  is 
particularly  valuable  because  it  expresses  the  newest  advances.  Every  phase  of 
the  subject  is  considered. 

Pennsylvania  Medical  Journal 

"  Dr.  N'orris  has  succeeded  in  presenting  most  comprehensively  the  present  knowledge  ol 
gonorrhea  in  women  in  its  many  phases.  The  present  status  of  serum  and  vaccine  therapy  is 
given  in  detail." 


Braasch's  Pyelography 

Pyelography.  By  William  F.  Braasch,  M.  D.,  The  Mayo  Clinic, 
Rochester,  Minn.  Octavo  of  323  pages,  with  296  pyelograms.  Cloth, 
$5.00  net. 

A   NEW   WORK 

Dr.  Braasch's  new  work  is  the  first  comprehensive  collection  of  the  various  types  of 
pelvic  outlines,  both  normal  and  pathologic.  You  get  here  296  skiagrams  of  the  renal  pel- 
vis and  ureter,  selected  from  several  thousand  plates  made  at  the  Mayo  Clinic.  These  pye- 
lograms, together  with  the  clear  descriptions,  constitute  an  admirable  aid  to  the  differential 
diagnosis  of  the  various  conditions  affecting  the  renal  pelvis.  The  characteristic  pelvic  out- 
line in  each  disease  is  first  shown  you  by  the  excellent  pyelograms;  then  Dr.  Braasch  inter- 
prets these  pyelograms  for  you  in  diagnostic  terms.  You  get  the  history  of  pyelography,  the 
exact  technic  (selection  of  the  medium,  preparation  of  solution,  method  of  injection,  sources 
of  error,  results),  the  normal  pelves,  the  various  pathologic  outlines,  and  the  outlines  in  con- 
genital anomalies.     It  is  a  most  complete  work. 


SAC.VBERS-     BOOKS    ON 


Barnhill   and  Wales' 
Modern   Otology 

A  Text=Book  of  Modern  Otology.  By  John  F.  Barnhill,  M.  D., 
Professor  of  Otology,  Laryngology,  and  Rhinology,  and  Earnest 
de  W.  Wales,  M.  D.,  Associate  Professor  of  Otology,  Laryngology, 
and  Rhinology,  Indiana  University  School  of  Medicine,  Indianapolis. 
Octavo  of  598  pages,  with  314  original  illustrations.  Cloth,  $5.50  net; 
Half  Morocco,  37.00  net. 

THE  NEW  (2d  i  EDITION 

The  authors,  in  writing  this  work,  kept  ever  in  mind  the  needs  of  the 
physician  engaged  in  general  practice.  It  represents  the  results  of  personal 
experience  as  practitioners  and  teachers,  influenced  by  the  instruction  given  by 
such  authorities  as  Sheppard,  Uundas  Graru,  Percy  Jakins,  Jansen,  and  Alt. 
Much  space  is  devoted  to  prophylaxis,  diagnosis,  and  treatment,  both  medical 
and  surgical.  There  is  a  special  chapter  on  the  bacteriology  of  car  affections — 
a  feature  not  to  be  found  in  any  other  work  on  otology.  Great  pains  have  been 
taken  with  the  illustrations,  in  order  to  have  them  as  practical  and  as  helpful  as 
possible,  and  at  the  same  time  highly  artistic.  A  large  number  represent  the 
best  work  of  Mr.  H.  F.  Aitken. 


Coolidg'e  on  Nose  and  Throat 

Manual  of  Diseases  of  the  Nose  and  Throat.  By  Algernon  Cool- 
Idge,  M.  D.,  Professor  of  Laryngology,  Harvard  Medical  School. 
Octavo  of  360  pages,  illustrated.     Cloth,  $1.50  net. 

This  new  book  furnishes  the  student  and  practitioner  a  guide  and  ready  reference  to  the 
important  details  of  examination,  diagnosis,  and  treatment.  Established  facts  are  empha- 
sized and  unproved  statements  avoided.  Anatomy  and  physiology  of  the  different  regions 
are  included. 

Frank  Allport,  M.  D. 

Professor  of  Otology,  Northwestern  University,  Chicago. 

"  I  regard  it  as  one  of  the  best  books  in  the  English  language  on  this  subject.  The 
pictures  are  especially  good,  particularly  as  they  are  practically  all  original  and  not  th-;  old 
reproduced  pictures  so  frequently  seen." 


DISEASES   OF   THE  EYE, 


DeSchweinitz's 
Diseases  of  the  Eye 

Just  Out— New    8th)  Edition 

Diseases  of  the  Eye:  A  Handbook  of  Ophthalmic  Practice. 
By  G.  E.  deSchweinitz,  M.D.,  Professor  of  Ophthalmology  in  the  Uni- 
versity of  Pennsylvania,  Philadelphia,  etc.  Handsome  octavo  of  754 
pages,  386  text-illustrations,  and  7  chromo-lithographic  plates.  Cloth, 
$6.00  net;  Sheep  or  Half  Morocco,  $7. 50  net. 

THE  STANDARD  AUTHORITY 

The  new  matter  added  includes:  Walker's  testing  of  visual  field,  squirrel 
plague  conjunctivitis,  swimming  bath  conjunctivitis,  anaphylactic  keratitis,  family- 
cerebral  degeneration  with  macular  changes,  ocular  symptoms  of  pituitary 
disease,  sclerectomy  with  a  punch,  preliminary  capsulotomy,  iridotasis,  thread 
drainage  of  anterior  chamber,  extraction  of  cataract  in  capsule  after  subluxation 
of  lens  with  capsule  forceps,  capsulomuscular  advancement  with  partial  resection, 
tenotomy  of  inferior  oblique,  window  resection  of  nasal  duct. 


Bass   and  Johns'   Alveolodental   Pyorrhea 

Alveolodental  Pyorrhea.  By  Charles  C.  Bass,  M.  D.,  Professor 
of  Experimental  Medicine,  and  Foster  M.  Johns,  M.  D.,  Instructor  in 
the  Laboratories  of  Clinical  Medicine,  Tulane  Medical  College.  Octavo 
of  168  pages,  illustrated.  Cloth,  $2.50  net. 

Drs.  Bass  and  Johns  present  their  subject  from  the  viewpoint  of  infection  by 
the  Endamceba  buccalis.  You  get  a  full  account  of  the  Endamceba  buccalis,  the 
history  of  disease,  the  morbid  processes,  contagiousness,  symptomatology,  how 
to  make  your  diagnosis  from  the  history  and  microscopic  examination,  prophy- 
laxis, and  the  exact  technic  for  using  emetin  hydrochlorid.  You  get  the  action 
of  emetin  upon  the  Endamceba,  you  get  the  exact  dosage,  you  get  the  interval 
between  doses,  the  local  effect,  the  urticaria  produced,  the  tecknic  of  injection. 

University  of  Pennsylvania  Medical  Bulletin 

"Upon  reading  through  the  contents  of  this  book  we  are  impressed  by  tne  remarkable 
fulness  with  which  it  reflects  the  notable  contributions  recently  made  to  ophthalmic  literature. 
No  important  subject  within  its  province  has  been  neglected." 


SAUNDERS'   BOOKS   ON 


GET  J*  *  THE  NEW 

THE    BEST  i\  1X1  6  r  1  C  £fc  II  STANDARD 

Illustrated   Dictionary 

New  (8th)  Edition— 1500  New  Terms 


The  American  Illustrated  Medical  Dictionary.  A  new  and  com- 
plete dictionary  of  the  terms  used  in  Medicine,  Surgery,  Dentistry, 
Pharmacy,  Chemistry,  Veterinary  Science,  Nursing,  and  kindred 
branches;  with  over  100  new  and  elaborate  tables  and  many  illustra- 
tions. By  W.  A.  Newman  Dorland,  M.D.,  Editor  of  "  The  American 
Pocket  Medical  Dictionary."  Large  octavo,  with  1 137  pages,  bound  in 
full  flexible  leather.     Price,  $4.50  net;  with  thumb  index,  $5.00  net. 

KEY  TO  CAPITALIZATION  AND  PRONUNCIATION— ALL  THE  NEW  WORDS 

This  dictionary  is  the  "new  standard."  It  defines  hundreds  of  the  newest 
terms  not  defined  in  any  other  dictionary — bar  none.  These  terms  are  live, 
active  words,  taken  right  from  modern  medical  literature. 

Howard  A.  Kelly,  M.  D., 

'  Professor  of  Gynecologic  Surgery,  Johns  Hopkins  University,  Baltimore 
"  Dr.  Dorland*s  Dictionary  is  admirable.     It  is  so  well  gotten  up  and  of  such  convenient 
size.     No  errors  have  been  found  in  mv  use  of  it." 


Theobald's  Prevalent  Eye  Diseases 


Prevalent  Diseases  of  the  Eye.  By  Samuel  Theobald,  M.  D., 
Clinical  Professor  of  Ophthalmology  and  Otology,  Johns  Hopkins 
University.  Octavo  of  55opages,  with  219  text-cuts  and  several  colored 
plates.     Cloth,  $4.50  net ;   Half  Morocco,  $6.00  net. 

THE    PRACTITIONER'S    OPHTHALMOLOGY 

With  few  exceptions  all  the  works  on  diseases  of  the  eye,  although  written 
ostensibly  for  the  general  practitioner,  are  in  reality  adapted  only  to  the  specialist  ; 
but  Dr.  Theobald  in  his  book  has  described  very  clearly  and  in  detail  those  condi- 
tions, the  diagnosis  and  treatment  of  which  come  within  the  province  of  the  general 
practitioner.  The  therapeutic  suggestions  are  concise,  unequivocal,  and  specific. 
It  is  the  one  work  on  the  Eye  written  particularly  for  the  general  practitioner. . 
Charles  A.  Oliver,  M.D., 

Cluneal  Professor  of  Ophthalmology,   Woman's  Medical  College  of  Pennsylvania. 

"  I  feel  I  can  conscientiously  recommend  it,  not  only  to  the  general  physician  and  medical 
student,  for  whom  it  is  primarily  written,  but  also  to  the  experienced  ophthalmologist.  Molt 
surely  Dr.  Theobald  has  accomplished  his  purpose." 


DISEASES   OF   THE  EYE. 


Haab  and  DeSchweinitz's 
External  Diseases  qf  the  Eye 


Atlas  and  Epitome  of  External  Diseases  of  the  Eye.     By  Dr.  O. 

Haab,  of  Zurich.  Edited,  with  additions,  by  G.  E.  DeSchweinitz, 
M.  D.,  Professor  of  Ophthalmology,  University  of  Pennsylvania.  With 
IOI  colored  illustrations  on  46  lithographic  plates  and  244  pages  of 
text.     Cloth,  $3.00  net.     In  Saunders  Maud-Atlas  Scries. 

THIRD  EDITION 

Conditions  attending  diseases  of  the  external  eye,  which  are  often  so  complicated, 
have  probably  never  been  more  clearly  and  comprehensively  expounded  than  in 
the  forelying  work,  in  which  the  pictorial  most  happily  supplements  the  verbal 
description.     The  price  of  the  book  is  remarkably  low. 

The  Medical  Record,  New  York 

"  The  work  is  excellently  suited  to  the  student  of  ophthalmology  and  to  the  practising 
physician.     It  cannot  fail  to  attain  a  well-deserved  popularity." 


Haab  and  DeSchweinitz V 
Ophthalmoscopy 


Atlas  and  Epitome  of  Ophthalmoscopy  and  Ophthalmoscopic 
Diagnosis.  By  Dr.  O.  Haab,  of  Zurich.  Edited,  with  additions,  by 
G.  E.  DeSchweinitz,  M.  D.,  Professor  of  Ophthalmology,  University 
of  Pennsylvania.  With  152  colored  lithographic  illustrations  and  92 
pages  of  text.  Cloth,  S3.00  net.  In  Saunders'  Hand-Atlas  Series. 
SECOND  EDITION 

The  great  value  of  Prof.  Haab's  Atlas  of  Ophthalmoscopy  and  Ophthalmo- 
scopii  Diagnosis  has  been  fully  established  and  entirely  justified  an  English 
translation.  Not  only  is  the  student  made  acquainted  with  carefully  prepared 
ophthalmoscopic  drawings  done  into  well-executed  lithographs  of  the  most  im- 
porcant  fundus  changes,  but,  in  many  instances,  plates  of  the  microscopic  lesions 
are  added.     The  whole  furnishes  a  manual  of  the  greatest  possible  service. 

The  Lancet,  London 

"  W'e  recommend  it  as  a  work  that  should  be  in  the  ophthalmic  wards  or  in  the  library  of 
every  hospital  into  which  ophthalmic  cases  are  received." 


SAUNDERS    HOOKS  ON 


Head's  Mouth  Infections 

Mouth  Infections.     By  Joseph  Head,  M.  D. ,  D.  D.  S.     Octavo  of 
35°  PaSesi  wfth  310  illustrations.  Ready  Soon. 

THE  RESULT  OF  30  YEARS'  ACTIVE  PRACTICE 

That  gum  and  tooth  infections  may  originate  valvular  heart  disease,  pernicious 
anemia,  arthritis  deformans,  rheumatism,  and  nervous  derangements  there  is  re- 
peated clinical  proof.  Dr.  Head,  a  specialist  in  this  field,  cites  case  after  case  of 
organic  diseases — just  such  cases  as  come  into  your  office  for  treatment  daily — 
which  he  has  traced  to  lesions  in  the  gums  due  to  infection,  and  cured  of  both  local 
and  systemic  affections.  He  gives  you  the  principles,  the  technic  in  full,  and  his 
original  formula;  and  methods.  You  get  sections  on  diagnosis,  treatment,  mouth 
hygiene,  local  anesthesia  by  novocain,  electrolysis,  tooth  discoloration,  care  of 
children's  teeth,  orthodontia,  cement,  .r-ray  study,  use  of  emetin,  and  of  vaccines. 
It  is  a  book  of  wide  and  varied  application,  of  vital  importance,  and  of  true  scien- 
tific value.  It  appeals  first  to  the  dentist  and  dental  surgeon,  but  it  appeals  strongly 
to  the  general  practitioner,  surgeon,  and  specialist  because  of  the  recognized  im- 
portance of  mouth  infections  as  factors  in  the  etiology  of  organic  disease. 


Kyle's 
Diseases  of  Nose  and  Throat 


Diseases  of  the  Nose  and  Throat.  By  D.  Braden  Kyle,  M.  D., 
Professor  of  Laryngology  in  the  Jefferson  Medical  College,  Phila- 
delphia. Octavo,  825  pages;  with  258  illustrations,  28  in  colors. 
Cloth,  $4.50  net;   Half  Morocco,  #>6.oo  net. 

THE  NEW  (5th)   EDITION 

The  new  (jtli)  edition  of  Dr.  Kyle's  work  shows  an  increase  of 100 pages and 
some  40  new  illustrations.  The  following  ne-u'  articles  have  been  added :  vaccine 
therapy  ;  lactic  bacteriotherapy;  salvarsan  in  the  treatment  of  syphilis  of  the  upper 
respiratory  tract  ;  sphenopalatine  ganglia  neuralgia  ;  negative  air-pressure  in  ac- 
cessory sinus  disease  ;  chronic  hyperplastic  ethmoiditis  ;  and  congenital  insuffi- 
ciency of  the  palate.  The  tables  of  differential  diagnosis  and  the  prescriptions  are 
striking  points  of  Dr.  Kyle's  book. 

Pennsylvania  Medical  Journal 

"  Dr.  Kyle's  crisp,  terse  diction  has  enabled  the  inclusion  of  all  needful  nose  and  throat 
knowledge  in  this  book." 


URINE  AND   IMPOTENCE. 


Og'den  on  the  Urine 


Clinical  Examination  of  Urine  and  Urinary  Diagnosis.  A  Clinical 
Guide  for  the  Use  of  Practitioners  and  Students  of  Medicine  and  Sur- 
gery. By  J.  Bergen  Ogden,  M.  D.,  Medical  Chemist  to  the  Metro- 
politan Life  Insurance  Company,  New  York.  Qctavo,  418  pages,  54 
text  illustrations,  and  a  number  of  colored  plates.     Cloth,  $3.00  net. 

THIRD  EDITION 

In  this  edition  the  work  has  been  brought  absolutely  down  to  the  present  day 
Urinary  examinations  for  purposes  of  life  insurance  have  been  incorporated,  because 
a  large  number  of  practitioners  are  often  called  upon  to  make  such  analyses. 
Special  attention  has  been  paid  to  diagnosis  by  the  character  of  the  urine,  the 
diagnosis  of  diseases  of  the  kidneys  and  urinary  passages  ;  an  enumeration  of  the 
prominent  clinical  symptoms  of  each  disease  ;  and  the  peculiarities  of  the  urine 
in  certain  general  diseases. 

The  Lancet,  London 

"  We  consider  this  manual  to  have  been  well  compiled  ;  and  the  author's  own  experience, 
5t>  clearly  stated,  renders  the  volume  a  useful  one  both  for  study  and  reference." 


Pilcher's 
Practical  Cystoscopy 

Practical  Cystoscopy.  By  Paul  M.  Pilcher,  M.  D.,  Consulting 
Surgeon  to  the  Eastern  Long  Island  Hospital.  Octavo  of  504  pages, 
with  299  illustrations,  29  in  colors.     Cloth,  $6.00  net. 

NEW  (2d     EDITION 

Cystoscopy  is  to-day  the  most  practical  manner  of  diagnosing  and  treating 
diseases  of  the  bladder,  ureters,  kidneys,  and  prostate.  To  be  properly  equipped, 
therefore,  you  must  have  at  your  instant  command  the  information  this  book  gives 
you.  It  explains  away  all  difficulty,  telling  you  why  you  do  not  see  something 
when  something  is  there  to  see,  and  telling  you  how  to  see  it.  All  theory  has 
been  uncompromisingly  eliminated,  devoting  every  line  to  practical,  needed- 
every-day  facts,  telling  you  how  and  when  to  use  the  cystoscope  and  catheter — 
telling  you  in  a  way  to  make  you  know.  The  work  is  complete  in  every  detail. 
Bransford  Lewis,  M.  D.,  Si.  Louis  University. 

"  I  am  very  much  pleased  with  Dr.  Pilcher's  '  Practical  Cystoscopy.'  I  think  it  is  the  best 
in  the  English  language  now." — April  rj,  ign. 


SAUNDERS"   BOOKS    ON 


Goepp's 
Dental   State   Boards 


Dental  State  Board  Questions  and  Answers By  R.  Max  Goepi 

M.  D.,  author  "  Medical  State  Board  Questions  and  Answers."     Octav 
of  428  pages.     Cloth,  $3.00  net. 

SECOND  EDITION 

This  new  work  is  along  the  same  practical  lines  as  Dr.  Goepp's  successful  wor 
on  Medical  State  Boards.  The  questions  included  have  been  gathered  from  reliabl 
sources,  and  embrace  all  those  likely  to  be  asked  in  any  State  Board  examinatio 
in  any  State.  They  have  been  arranged  and  classified  in  a  way  that  makes  for 
rapid  resume  of  every  branch  of  dental  practice,  and  the  answers  are  couched  i 
language  unusually  explicit — concise,  definite,  accurate. 

The  practicing  dentist,  also,  will  find  here  a  work  of  great  value — a  wor 
covering  the  entire  range  of  dentistry  and  extremely  well  adapted  for  quic 
reference. 


Haab  and  deSchweinitz's 
Operative  Ophthalmology 

Atlas  and   Epitome  of    Operative    Ophthalmology.       By  Dr.  C 

Haab,  of  Zurich.  Edited,  with  additions,  by  G.  E.  deSchweinit: 
M.  D.,  Professor  of  Ophthalmology  in  the  University  of  Pennsylvani; 
With  30  colored  lithographic  plates,  154  text-cuts,  and  375  pages  0 
text.     In  Saunders'  Hand-Atlas  Series.     Cloth,  $3.50  net. 


Dr.  Haab's  Atlas  of  Operative  Ophthalmology  will  be  found  as  beautiful  an 
as  practical  as  his  two  former  atlases.  The  work  represents  the  author' s  thirl 
years'  experience  in  eye  work.  The  various  operative  interventions  are  describe 
with  all  the  precision  and  clearness  that  such  an  experience  brings.  Recognizin 
the  fact  that  mere  verbal  descriptions  are  frequently  insufficient  to  give  a  clej 
idea  of  operative  procedures,  Dr.  Haab  has  taken  particular  care  to  illustral 
plainly  the  different  parts  of  the  operations. 

Johns  Hopkins  Hospital  Bulletin 

"  The  descriptions  of  the  various  operations  are  so  clear  and  full  that  the  volume  can  w< 
hold  place  with  more  pretentious  text-books." 


GENITO-URINARY  AND    NOSE,     THROAT,     ETC.  u 

Greene  and  Brooks' 
Genito-Urinary  Diseases 

Diseases  of    the   Genito-Urinary   Organs  and  the   Kidney.      By 

Robert  H.  Greene,  M.  D.,  Professor  of  Genito-Urinary  Surgery  at 
Fordham  University;  and  Harlow  Brooks,  M.  D.,  Assistant  Pro- 
fessor of  Clinical  Medicine,  University  and  Bellevue  Hospital  Medical 
School.  Octavo  of  639  pages,  illustrated.  Cloth,  $5.00  net;  Half 
Morocco,  $6.50  net. 

THIRD  EDITION 

This  new  work  presents  both  the  medical  and  surgical  sides.  Designed  as  a 
work  of  quick  reference,  it  has  been  written  in  a  clear,  condensed  style,  so  that 
the  information  can  be  readily  grasped  and  retained.  Kidney  diseases  are  very 
elaborately  detailed. 

New  York  Medical  Journal 

"  As  a  whole  the  book  is  one  of  the  most  satisfactory  and  useful  works  on  genito-urinar» 
diseases  now  extant,  and  will  undoubtedly  be  popular  among  practitioners  and  students." 

Gleason  on  Nose,  Throat, 
and  Car 

A   Manual   of    Diseases  of   the    Nose,  Throat,  and    Ear.     By  E. 

Baldwin  Gleason,  M.  D.,  LL.  D.,  Professor  of  Otology,  Medico- 
Chirurgical  College,  Graduate  School  of  Medicine,  University  of  Penn- 
sylvania.     1 21110  of  590  pages,  profusely  illustrated.     Cloth,  $2.75  net. 

THIRD    EDITION 

Methods  of  treatment  have  been  simplified  as  much  as  possible,  so  that  in 
most  instances  only  those  methods,  drugs,  and  operations  have  been  advised 
which  have  proved  beneficial.  A  valuable  feature  consists  of  the  collection  of 
formulas. 

American  Journal  of  the  Medical  Sciences 

"  For  the  practitioner  who  wishes  a  reliable  guide  in  laryngology  and  otology  there  are  few 
books  which  can  be  more  heartily  commended." 


SAUNDERS'   BOOKS  ON 


Holland's  Medical 
Chemistry  and  Toxicology 

A  Text-Book  of  Medical  Chemistry  and  Toxicology.  By  James 
W.  Holland,  M.  D.,  Emeritus  Professor  of  Medical  Chemistry  and 
Toxicology,  and  Dean,  Jefferson  Medical  College,  Philadelphia.  Octavo 
of  678  pages,  fully  illustrated.     Cloth,  $3.00  net. 

FOURTH  EDITION 

Dr.  Holland's  work  is  an  entirely  new  one,  and  is  based  on  his  forty  years' 
practical  experience  in  teaching  chemistry  and  medicine.  It  has  been  subjected  to 
a  thorough  revision,  and  enlarged  to  the  extent  of  some  sixty  pages.  The  additions 
to  be  specially  noted  are  those  relating  to  the  electronic  theory,  chemical  equilib- 
rium, Kjeldahl's  method  for  determining  nitrogen,  chemistry  of  foods  and  their 
changes  in  the  body,  synthesis  of  proteins,  and  the  latest  improvements  in  urinary 
tests.     More  space  is  given  to  toxicology  than  in  any  other  text-book  on  chemistry. 

American  Medicine 

'"  Its  statements  are  clear  and  terse  ;  its  illustrations  well  chosen;  its  development  logical, 
systematic,  and  comparatively  easy  to  follow.  .  .  .  We  heartily  commend  the  work." 

Ivy's  Applied  Anatomy  and 

Oral  Surgery  for  Dental  Students 


Applied    Anatomy  and    Oral    Surgery  for  Dental  Students.     By 

Robert  H.  Ivy,  M.D.,  D.D.S.,  Assistant  Oral  Surgeon  to  the  Philadel- 
phia General  Hospital.  i2mo  of  280  pages,  illustrated.  Cloth,  $1. 50 
net. 

FOR  DENTAL  STUDENTS 

This  work  is  just  what  dental  students  have  long  wanted — a  concise,  practical 
work  on  applied  anatomy  and  oral  surgery,  written  with  their  needs  solely  in 
mind.  No  one  could  be  better  fitted  for  this  task  than  Dr.  Ivy,  who  is  a  graduate 
in  both  dentistry  and  medicine.  Having  gone  through  the  dental  school,  he 
knows  precisely  the  dental  student's  needs  and  just  how  to  meet  them.  His 
medical  training  assures  you  that  his  anatomy  is  accurate  and  his  technic  modern. 
The  text  is  well  illustrated  with  pictures  that  you  will  find  extremely  helpful. 

H.  P.  Kuhn,  M.D.,  Western  Dental  College,  Kansas  City. 

"  I  am  delighted  with  this  compact  little  treatise.     It  seems  to  me  just  to  fill  the  bill." 


CHEMISTRY,   SKIN,   AXD    VENEREAL   DISEASES.  IJ 

American  Pocket  Dictionary  New  9th i  Edition 

The  American  Pocket  Medical  Dictionary.  Edited  by  W.  A. 
Newman  Dorland,  M.  D.,  Editor  "American  Illustrated  Medical 
Dictionary."  Containing  the  pronunciation  and  definition  of  the 
principal  words  used  in  medicine  and  kindred  sciences.  693  pages. 
Flexible  leather,  with  gold  edges,  $1.25  net;  with  thumb  index, 
$1.50  net. 

James  W.  Holland.  M.  D., 
■  Professor  of  Medical  Chemistry  and  Toxicology,  and  Dean,  Jefferson  Medical  College 

Philadelphia, 
"  I  am  struck  at  once  with  admiration  at  the  compact  size  and  attractive  exteripr.     ) 
rtmend  it  to  our  students  without  reserve." 


Stelwagon's  Essentials  of  Skin  7th  Edition 

Essentials  of  Diseases  of  the  Skin.  By  Henry  W.  Stel- 
WAGON,  M.  D.,  Ph.D.,  Professor  of  Dermatology  in  the  Jeffer- 
son Medical  College,  Philadelphia.  Post-octavo  of  291  pages, 
with  72  text-illustrations  and  8  plates.  Cloth,  $1.25  net.  In 
Saunders'   Question-  Compend  Series. 

The  Medical  News 

"  In  line  with  our  present  knowledge  of  diseases  of  the  skin.  .  .  .  Continues  to  main- 
tain the  high  standard  of  excellence  for  which  these  question  compends  have  been  noted." 

Wolffs  Medical  Chemistry  seventh  Edition 

Essentials  of  Medical  Chemistry,  Organic  and  Inorganic. 
Containing  also  Questions  on  Medical  Physics,  Chemical  Physiol- 
ogy, Analytical  Processes,  Urinalysis,  and  Toxicology.  By  Law- 
rence Wolff,  M.  D.,  Late  Demonstrator  of  Chemistry,  Jefferson 
Medical  College.  Revised  by  A.  Ferree  Wit.mer,  Ph.  G.,  M.  D., 
Formerly  Assistant  Demonstrator  of  Physiology,  University  of 
Pennsylvania.  Post-octavo  of  222  pages.  Cloth,  §1.25  net.  In 
Saunders'  Question-Compeud  Series. 

Vecki's  Sexual  Impotence  New  sth  Edition 

Sexual  Impotence.  By  Victor  G.  Vecki,  M.  D.,  Consulting 
Genito-Urinary  Surgeon  to  Mt.  Zion  Hospital,  San  Francisco. 
i2mo  of  405  pages.     Cloth,  $2.25  net. 

Johns  Hopkins  Hospital  Bulletin 

"A  scientific  treatise  upon  an  important  and  much  neglected  subject.  ...  The 
treatment  of  impotence  in  general  and  of  sexual  neurasthenia  is  discriminating  and 
judicious." 

Wilcox  on  Genito-Urinary  and  Venereal  Diseases 

Second  Edition 

Essentials  of  Genito-Urinary  and  Venereal  Diseases.  By 
Starling  S.  Wilcox,  M.  D.,  Lecturer  on  Genito-Urinary  Diseases 
and  Syphilology,  Starling-Ohio  Medical  College,  Columbus.  121110 
of  321  pages,  illustrated.     Cloth,  $1.25  net.     Saunders' Compends. 


SA  UN  VERS'    BOOKS   ON 


Second 
Edition 


Wells'   Chemical  Pathology 

Chemical  Pathology.  Being  a  discussion  o<  General  Path- 
ology from  the  Standpoint  of  the  Chemical  Processes  Involved. 
By  H.  Gideon  Wells,  Ph.  D.,  M.  D.,  Assistant  Professor  of 
Pathology  in  the  University  of  Chicago.  Octavo  of  616  pages. 
Cloth,  $3.25  net. 

Wm.   H.  Welch,  M.  D..  Professor  of  Pathology,  Johns  Hopkins  University. 

"The  work  fills  a  real  need  in  Ihe  English  literature  of  a  very  important  subject,  and 
I  shall  be  glad  to  recommend  it  to  my  students." 


Fourth 
Revised  Edition 


Jackson's  Essentials  of  Eye 

Essentials   of   Refraction    and    of    Diseases   of   the    Eye.     By 

Edward  Jackson,  A.  M.,  M.  D.,  Emeritus  Professor  of  Diseases  of 
the  Eye,  Philadelphia  Polyclinic.  Post-octavo  of  261  pages,  82  illus- 
trations.    Cloth,   $1.25   net.      In  Saunders'  Question-Corn  pend  Series. 

Johns  Hopkins  Hospital   Bulletin 

"  The  entire  ground  is  covered,  and  the  points  that  most  need  careful  elucidation  are. 
made  clear  and  easy." 

Gleason's  Nose  and  Throat     Fourth  SSS 

Essentials  of  Diseases    of  the    Nose   and    Throat.     By  E.   B. 

Gleason,  S.  B.,  M.  D.,  Clinical  Professor  of  Otology,  Medico- 
Chirurgical  College  ;  Graduate  School  of  Medicine,  University  of 
Pennsylvania.  Post-octavo,  241  pages,  1 12  illustrations.  Cloth. 
$1.25   net.      /;/  Saunders'  Question  Compends. 

The  Lancet,  London 

"  The  careful  description  which  is  given  of  the  various  procedures  would  be  sufficient 
to  enable  most  people  of  average  intelligence  and  of  slight  anatomical  knowledge  to  make 
a  very  good  attempt  at  laryngoscopy." 

Grunwald  and  Grayson  on  the  Larynx 

Atlas  and   Epitome  of   Diseases    of  the  Larynx.     By  Dr.   L. 

Grunwald,  of  Munich.  Edited,  with  additions,  by  Charles  P. 
Grayson,  M.D.,  University  of  Pennsylvania.  With  107  colored 
figures  on  44  plates,  25  text-cuts,  and  103  pages  of  text.  Cloth, 
$2.50  net.     In  Saunders'  Hand-Atlas  Series. 


Second 
Edition 


Mracek  and  Stelwagon's  Atlas  of  Skin 

Atlas  and  Epitome  of  Diseases  of  the  Skin.  By  Prof.  Dr. 
Franz  Mracek,  of  Vienna.  Edited,  with  additions,  by  Henry 
W.  Stelwagon,  M.D.,  Jefferson  Medical  College.  With  77  col- 
ored plates,  50  half-tone  illustrations,  and  280  pages  of  text.  In 
Saunders'  Hand-Atlas  Series.     Cloth,  $4 .00  net. 


EYE,    EAR,    NOSE,    AND    THROAT. 


deSchweinitz    and    Holloway   on   Pulsating    Exoph- 
thalmos 

Pulsating  Exophthalmos.  An  analysis  of  sixty-nine  cases  not  pre- 
viously analyzed.  By  George  E.  deSchweinitz,  M.  D.,  and  Thomas 
B.  Holloway,  M.  D.     Octavo  of  125  pages.     Cloth,  $2.00  net. 

This  monograph  consists  of  an  analysis  of  sixty-nine  cases  of  this  affection 
not  previously  analyzed.  The  therapeutic  measures,  surgical  and  otherwise, 
which  have  been  employed  are  compared,  and  an  endeavor  has  been  made 
to  determine  from  these  analyses  which  procedures  seem  likely  to  prove  of 
the  greatest  value.  It  is  the  most  valuable  contribution  to  ophthalmic  liter- 
ature within  recent  years. 

British  Medical  Journal 

ith  the  whole  subject  and  in  it  the  most  complete  account  of 

Jackson  on  the   Eye  Preparin(,  New  (3d)  Edition 

A  Manual  of  the  Diagnosis  and  Treatment  of  Diseases  of  the 
Eye.  By  Edward  Jackson,  A.  M.,  M.  D.,  Professor  of  Ophthalmology, 
University  of  Colorado.  i2mo  volume  of  615  pages,  with  1S4  beautiful 
illustrations. 

The  Medical  Record,  New  York 

"  It  is  truly  an  admirable  work.  .  .  .  Written  in  a  clear,  concise  manner,  it  bears  evidence  of  the 
author's  comprehensive  grasp  of  the  subject.  The  term  '  multum  in  parvo'  is  an  appropriate  one  to 
apply  to  this  work." 

Grant  on   Face,   Mouth,   and   Jaws 

A  Text-Book  of  the  Surgical  Principles  and  Surgical  Diseases 
of  the  Face,  Mouth,  and  Jaws.  For  Dental  Students.  By  H.  Horace 
Grant,  A.  M.,  M.  1).,  Professor  of  Surgery  and  of  Clinical  Surgery, 
Hospital  College  of  Medicine,  Louisville.  Octavo  of  231  pages,  with 
6S  illustrations.     Cloth,  $2.50  net. 

Preiswerk  and  Warren's  Dentistry 

Atlas  and  Epitome  of  Dentistry.  By  Prof.  G.  Preiswerk,  of 
Basil.  Edited,  with  additions,  by  George  W.  Warren,  D.D.S.,  Pro- 
fessor of  Operative  Dentistry,  Pennsylvania  College  of  Dental  Surgery, 
Philadelphia.  With  44  lithographic  plates,  152  text-cuts,  and  343  page3 
of  text.      Cloth.  $3. 50  net.     In  Saunders*  Atlas  Series, 

Asher's  Chemistry  and  Toxicology 

Chemistry  and  Toxicology  for  Nurses.  By  l'mi  ir  Asher,  Ph.G., 
M.  D.,  Dean  and  Professor  of  Chemistry,  New  Orleans  College  of  Phar- 
macy.     i2mo  of  190  pages.     Cloth,  $1.25  net. 


Date 

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